My note 4 review after 4 months. Jumped from Xperia Z.
- Before Root got about 3.5hours SOT. After root + Greenify + change browser to CM browser = 6 - 7 hours SOT.
- TBH, this is my first Samsung and I find Touchwiz to be feature packed and snappy. The exynos chip and 3gb ram can be thanked for that. Gain root and remove the bloatware.
- Note4 confirm has signal issues. A user claiming to be a network technician said N4 was underwhelming in their tests. However, just because you don't have a full bar, doesn't necessarily mean the data speed is bad. Just means signal may change from H+ to 3G easier. I found by selecting only WDCMA/GSM instead with LTE, I have a slightly more stable signal. Overall disappointed this area of phone.
- I use celcom line and have not encountered drop calls like some digi customers.
- Phone heat during heavy usage is fine by my standards, try holding an Xperia Z while playing a graphic intensive game,  now that is HOT.
- if u really want to save batt, stop using Chrome browser.  Dolphin and CM browser really makes a difference. Just needs getting used to. 
- If you have poor signal issues, advisable not to use a bumper with metal or aluminium. It is known to affect signal reception. First made known in xda forums with the verus iron shield.
- Camera is a freaking beast. My most loved feature in this phone. If free, will post some photos. In fact others should to.
- Love the Spen. Use it to make notes and have a lot of fun making doodles on photos of friends.
- Bluetooth works well, listening beat music via wireless earphones while shopping in Tesco is priceless.
- Screen quality is really amazing. If you upgrading from 2/3 ++ year old phone, be prepared to pamper your eyes.
- For me sound from rear speaker is pretty ok and loud but only when it's not laid on its back or covered up.
- For a big phone, the vibration when phone rings or from notifications is not strong enough.
- I find the autobrightness sensor to be not fast enough to detect changes to ambient lighting but it definately has a great wide range of brightness to select.
- Fast charging is OMG! Where have you been all this while?
- If you are facing buggy IR blaster, uninstall all updates to get it to work again.
- Really cool mobile multimedia consumption device - games, movies, shows, music.
That's all I can think off. If you can afford this phone, and live in an area with good network reception, then go ahead and buy this phone.