1. Notification Center: New Notification System
2. Improved app notifications at the top
3. Lock screen notifications. Swipe will open related app.
4. Notification options to choose for each app.
5. Notification sorting by app, time etc.
6. iMessage: Text messaging between iOS devices over Wi-Fi or 3G (Similar to WhatsApp)
7. Newstand: Similar to iBooks to store, auto-download magazine subscriptions & new issues.
8. Reminders: A list of reminders with Geo-fence integrated with Calendar app
9. Twitter Integration: Log in to Twitter from settings once and Tweet anything from Safri, Photos, YouTube etc. Similar to login & sharing used by Mail.app
10. AirPlay Mirroring for iPad 2: Duplicate the iPad screen on television wirelessly
11. iCloud integration: A new free service with more than 5GB data to be shared between iOS devices
12. Open Camera.app from lock screen: Double tapping on Home button will open the Camera.app from lock screen
13. Take pictures from lock screen: Volume up button can be used to take pictures
14. Camera Grid: For more precise focus and accurate photography. This feature was available on Camera+ app
15. Camera Zoom: Pinch-to-zoom Gesture like Photos.app on Camera.app
16. One tap Auto Focus and Auto Exposure
17. Lock Auto Exposure & Auto Focus for consistency.
18. Swipe Left to open camera roll
19. Crop Photos: Not available on 3GS
20. Enhance Color tones of photos: Not available on 3GS
21. Rotate Photos:
22. Red-eye removal: Remove, correct Red-eye within Photos.app
23. Photo Stream via iCloud over all your iOS devices
24. Organize photos within Camera Roll
25. Tabbed Browsing in Safari: For iPad only
26. Safari Reader: Like RSS reader
27. Safari Reading List: Save web pages for offline reading
28. Improved Performance: Like it was enhanced in 4.3.3
29. Private Browsing: Similar to Firefox / Incognito on Chrome.
30. Website specific data can be deleted
31. Cut the cord: Activate and setup iOS device without a Mac or PC
32. Over-The-Air (OTA) iOS Software Updates: Again, no need of a computer & cord
33. Delta Software Updates: Upgrade only changed files. No need to download & install entire OS. (Similar to WordPress!)
34. Wi-Fi Sync: Sync iOS device with PC or Mac over Wi-Fi
35. Backup and Restore from iCloud account
36. Sync Exchange tasks
37. Downloads: See a list of downloaded apps from App Store from any of your iOS device
38. Rich Text Formatting for Composing Mail (Bold, Italics, Underline, etc.)
39. Improved offline support for Mail.app
40. Indentation Control
41. Drag-able email addresses: Drag, arrange email addresses in To, CC, BCC fields
42. Improved mail search: Full content search in Mail
43. Flag Emails
44. S/MIME Security
45. Profile picture for Game Center
46. Friend recommendations for Game Center
47. Games recommendation
48. Friends-of-friends list
49. App Store in Game Center: App store integrated within Game Center to find & buy new Apps / Games
50. New Achievements like Perks, Points
51. Play turn-based games within Game Center
52. Swipe-Up with 4-5 fingers for multitasking bar (iPad only)
53. Swipe-Left or Swipe-Right with 4-5 fingers to switch between running apps (iPad only)
54. Pinch with 4-5 fingers for the home screen (iPad only)
55. New Split keyboard: For easier typing on iPad
56. New Keyboard Shortcuts (Not sure what it is)
57. Emoji Emoticons: Emoticons like we see in IMs now for iOS devices. Mostly with iMessage!
58. LED Flash for incoming calls and notifications for better accessibility
59. Custom vibration for incoming calls for better accessibility
60. VoiceOver improvements including custom element labeling
61. Custom tones for Calendar events
62. Custom tone for Received Mail
63. Custom tone for Sent mail
64. Custom tone for Voice-mail
65. Year view on Calendar: iPad only
66. Week view on Calendar: For iPhone & iPod
67. New Music App: Redesigned only for iPad
68. Music & Video: Two separate apps for iPhone (Instead of Video inside iPod app)
69. Scroll for long song titles
70. Song description: Tap & hold on a song title for description
71. Smart Playlists: Sync smart playlists from iTunes.
72. Weather Forecasts updates hourly
73. On-location Weather: Determines current location. Custom locations can be added/
74. Alternate routes in Maps
75. Print Maps: Print location, direction maps
76. Twitter Pictures: Use Twitter pictures for contacts with integrated Twitter
77. Auto Download in background: Newstand issues, apps can be downloaded in background once subscribed.
78. Sync in background: Now possible to use iOS device while it is still syncing in background
79. Links in background: Safari links, iTunes links can be opened in background
80. Space usage: Determine space used by each app, supported file types under settings
81. iCloud usage: Determine space used on iCloud under settings
82. Change device name: Change iOS device name on-the-go via settings
83. Some GUI Improvements
84. Personal Dictionary: Create & store own words for re-use
85. Built-in Dictionary: Built-in dictionary app
86. iTunes Tone Store: Choose, Buy, Install custom tones
87. Improved FaceTime video quality
88. VoiceOver Item Chooser
89. Speak Text:Speak text based on selection
90. Delete recent calls: Delete single or one-by-one recent call list
91. Delete app data: Delete saved games, saved data for specific apps / games
92. Time mid-call invitation alerts
93. Download Multiple Apps: Now its possible to download and install multiple apps instead of one-by-one.
94. Delete songs: Check to Delete songs / playlists on iOS device (It’s already possible I guess in 4.3.3 or its here on my phone only for me? )
95. New Keyboard Shortcuts: Type OMG and it will type Oh My God.
96. Custom Text Tones: Custom SMS tones. (Yeah, I think it’s there)
97. Auto Sync backup: It takes backup of the file on the device. Hence restoring from scratch is made easy. No need to grab all apps one-by-one. Saves lot of time.
98. ‘Install’ link instead of Price if the app is already bought.
99. Silent Switch: Shows volume level along with the Bell icon while switching back from Silent to Ringer (Currently it shows only the Bell icon)
100. Hotmail accounts have new icons & folders
101. Sync events, contacts, notes with predefined accounts under Mail.app (Like Hotmail, Gmail etc)
102. Marked Apps: All apps that are downloaded on iOS device for your account are marked as FREE (Free to download if they’re & free to download because you’ve already purchased them)
103. Arabic language support for VoiceOver
104. Icon Badges: Option to turn ON or OFF icon badges for apps. (Red circle with update)
105. Accessible input for mobility
106. Assistive Touch Gestures: Allows us to use iPhone with adaptive accessories while controlling touch sensitivity.
107. FaceTime over 3G: Yes, it is now possible. Not yet available for developers though.
108. Unsecured call notifications: I am not sure why does this prompt for confirmation for calls saying network is not encrypted! (Is this a feature or incomplete program?)
109. Mid-call Invitation Alert: If the phone is busy, we can still receive a placed conference call (Description is my interpretation)
110. Free @me.com email address: Yes. With iCloud integration, all iOS 5 users will get @me.com email ID
111. Custom Gestures: Create and save custom gestures. Mainly for motor-disables persons for use with AssistiveTouch accessories
112. Swipe-Left can let you browse through day-view one-by-one in Calendar
113. FaceTime without Sim card: FaceTime can now be activated and used either via a phone number or email address (Apple ID)
114. Unknown Caller details: When received a call from number that is not on contacts – the display also shows city name associated with the area code. Currently it shows in recent calls list only (I think I have seen this feature before on 4.2.1. Did you? )
115. Vibrate Alert for sent & received emails (What is they come-and-go the same time? Confusing?)
116. Real-TIme stock updates
117. Multiple Mark Read: Can now select & mark multiple emails as read.
118. Pause Timer: It’s possible to pause the Timer instead of ‘Cancel’
119. New German Keyboard: Easy access to Germanic umlaut
120. 1080p Playback support for iPad. (Awesome)
121. Social Networking Integration: Facebook, Flickr, LinkedIn, MySpace along with Twitter (Options under Settings.app but not sure if integrated throughout the OS like Twitter)
122. Headphone Balance: Option to choose Left & Right balance for headphones under Accessibility
123. Mono audio option for headphones under accessibility (except to choose balance as mentioned above)
124. Cellular Network for App Store: Option to Enable or Disable using Cellular Network (GPRS, 3G) to download apps from the App Store. (This is excellent!)
125. Disable In-App Purchase: Ability to completely disable In-App purchases
126. iTunes Password Prompt: It is now possible to set frequency for iTunes Password prompt to appear.
127. Storage Usage Clean Up: We can not only see what files have taken up the space but we can empty that space with single wipe like Apps, Game’s saved data, Music, Videos etc.
128. Equalizer Presets: These are now more BASS oriented (Most likely)
129. Improved Sound Check for music
130. RSA ID is now available when setting up VPN. (Thanks @jaytrixz for this update). This is for performing two-factor authentication for a user to a network resource.
131. Folders for Mail: Yes. Possible for any allowed mail account including new Hotmail. (I mentioned about Hotmail above but this is new feature for all accounts & thanks @Karl for this info)
132. Hide Keyboard: Hide (Dismiss) keyboard button whenever necessary. (This is for iPad only. Not for iPhone. Confirmed)
133. Find My iPhone: This is available as a part of iCloud integration with an option to disable it. (Thanks Michael for confirmation)
134. Scrolling Titles for YouTube videos
135. Double tap the home button on YouTube while watching a video to see who uploaded that video (Thanks @JohnothanVincentCrook for pointing it out)
136. HD YouTube video if connected to 3G
137. Option to disable HQ (HD) video playback over 3G
138. Take pictures using headphone remote: If you have headphone with remote them it is possible to take picture using Volume UP button. (Very useful if you have a tripod. Please confirm if anyone saw this!)
139. Animated GIF image support for iMessage. Does not animate in Photos.app
140. Hold and drag events from within different dates or time
141. Tapping and holding back button in Safari will show-up visited website history (iPad only)
142. Current time on Calendar if in landscape mode
143. New voices for Voice-Over
144. Option to display Stock & Weather widgets in Notification Center
145. Add family relations to contacts.
146. Restrictions with password required for purchases if enabled
147. Enable / Disable option for voice-dial if the phone is set to security with pass-code lock.
148. Purchase history on app store
149. Automatically set time for iPod Touches
150. Auto Correct & Spell Check are independent options.
151. Broadcast song information on devices (like car stereo) when connected over Bluetooth
152. New keyboard with prominent #(hash-tag) and @ (mention) buttons for Twitter app like we have a prominent ‘.com’ button for Safari address bar.
153. iPod app renamed to Music: How could I missed it writing here! It’s there on a screenshot on other post here
154. Enhanced Mail.app even in offline mode and sync back when online (like for deleted emails)
155. Help center: Learn more about every option under settings app to explore more about it (like Nokia has?)
156. New notification alerts within mail app if you forgot to write a subject line (Similar to Gmail!)
157. Hourly Weather Forecasts: Tap the current day and it will display hour-by-hour weather forecast. (This is separate from hourly weather update mentioned above)
158. En dash (–): Tap and hold hyphen (-) key to see & insert En dash. Em dash is already there. (Know more here about En & Em Dash)
159. Third-party Cables: Support for almost all third-party TV-out cables. No need to download Resupported from Cydia. This would be one of the major features if true. (Can someone without jailbroken iPhone confirm this?)
160. Choose Notification Type: Banner notifications or the classic pop-up notifications (for each app)
161. Mail Sidebar: Can be swiped in or out
162. Install Twitter from Settings app (Twitter integration as one feature each? see below points)
163. Tweet Location: in Maps
164. Tweet Picture: from the camera roll
165. Tweet Website URL: from Safari
166. Tweet Video: from YouTube
167. Backup homescreen layout on iCloud (Please confirm)
168. Backup app data on iCloud (Like game saves etc)
169. Backup purchased music, apps, and books on iCloud
170. Backup SMS and MMS
171. Backup ringtone(s)
172. Backup contacts
173. Schedule daily OTA (Over the air) iCloud backup
174. Message / iMessage: Repeat alerts up to 10 times
175. iOS crash reports to Apple with options: Send automatically or Don’t send.
176. Nuance Speech to Text: Not available in current beta but the most anticipated feature in final release. See concept here.(Speech Recognition)
177. Sync bookmarks, highlight from iBooks across devices
178. iMessages show a blue colored bubble to easily distinguish
179. Group messaging in iMessage
180. Delivery Reports
181. Read receipts for iMessage (enable from Settings)
182. See if other person is typing in iMessage (like in IMs)
183. Add Social Media info in to contacts
184. New rounded toggle switch
185. New separate Video app & icon
186. Nitro JavaScript speed improvements for Web Apps
187. iMessage will be sent as a text message in case iMessage is not available
188. Custom vibration for each contact so each pattern can let know who’s calling
189. New ‘Message’ option for iPod Touch under settings to use iMessage using an email ID
190. Setup AirPort device
191. Maximum recent email messages limit to 1000 instead of 200
192. Create & manage photo albums within Photos.app on device itself. (How did I miss this before? Thanks Joaquin for letting me know.)
193. (Custom) gesture-based lock-screen (Ability to define a custom gesture to unlock iPhone without need of a pass-code. This is not confirmed but rumored to be included in later releases of iOS 5. Do you see any benefit?)
194. Double tap the home button on lock screen to launch YouTube videos (Received an email about it. It was nice to have double tapping to play music. Why would they change? Someone please confirm if this is correct ) This is not correct. Instead it gives iPod controls and Take picture from camera options. Thanks JohnothanVincentCrook for confirming this.
195. SMS tones sound like they have been shortened than those were provided on iPhone 4 (Anyone felt it that way?)
196. While reading an email – swiping right would open a list of messages and swipe left would bring back to the open email message again. (Like if you’re reading an email from Inbox, it will take you to Inbox)
197. If you have multiple email accounts configured in Mail.app – swipe left or right from one’s mailboxes folder list, it will take you to another account’s mailboxes. (from Google Mail to Hotmail or back)
198. iTunes App: Support for match & find songs based on previous song purchases.
199. Free upgrade to 256 kbps bit-rate for purchased songs if backing up on iCloud
200. Support for multiple audio devices (Could not understand exact meaning of this)
201. Mirror iPhone 4 on Apple TV (Someone with Apple TV please confirm)
202. Skip tracks by swiping left – right on album art itself when not on lock screen (iPad only)
203. The name of the person that respond, appears in small light blue text directly above the response when SMS is sent to a group. (Thanks Melvin Baskin for emailing this)
204. Drag Keyboard on iPad: Drag keyboard up / down the screen wherever it is needed. It works for split keyboard as well.