Listing all changes, to start things off these are two things I noticed already:
Black Lion Chests have new icons
The in / out of range indicators have been changed (red bar or circle = out of range)
\Chain skills are all shown on skillbar when you hover over it, as are stealth skills when playing thief.
All food now gives an xp buff.

Mesmer changes:
Scepter Ether Clone (3rd hit): increased from a .6 multiplier to a .75 multiplier
Scepter Illusionary Counter: counter effect damage multiplier increased from 1 to 2.
Greatsword Bouncing Blade: now applies 3 stacks of might when it hits an ally;
increased might duration from 5 seconds to 10; increased damage multilier from .9 to 1.3
Greatsword Mind Stab: increased vulnerability duration from 6 seconds to 10 seconds; Mind Stab can now hit multiple targets.
Staff Illusionary Warlock: reduced his cooldown from 4 seconds to 2 seconds; increased the damage multiplier from .4 to .6
Staff Chaos Armor: Now always applies protection for 5 seconds when applied, and now applies swiftness randomly when hit instead of protection.
Staff Chaos Storm: decreased the recharge from 40 seconds to 30 seconds.
Necromancer minions have an option to auto attack enemies and the AI has improved
If bound, Mouse 4 and Mouse 5 etc. now show as M4 and M5 instead of "..."
if your individual keybinds where modified (e.g. shift+1) it now shows both, modifier and key whereas last stresstest it only showed "..."
Tooltip for how to make an ability autocast.
Your mouse pointer is now red when hovering over enemies
You can link merchant items in chat
Water drops on your screen after getting out of water are back!
you can now hit F after looting to loot all
stability from Death Shroud is now 3 seconds
You can change skin colour in the first page of character select
Waypoints that are on your map but not unlocked will show up bigger when zooming out.
If an ability has more then 1 step/phase the tooltips of all those steps and phases are shown
Orb of power work once again.
They removed the forced "downed state" from the starting boss encounter
Illusions shatter much faster.
Walk is now a toggle
You now have an option to get gems via "redeem code" in the store.
Cannons in The Mists are broken.
A new vista has been added to Lion's Arch (near the Arenanet Logo)
Icons of capturepoints in sPvP have been changed to be seen much better from distance on the screen. They are now less transparent.
Engineer shield seems to work now. (the knockback)
The 3rd hit on spirit hammer now causes a knock back similar to smite instead of a knock down.
Signets now tell you the exact value of their passive stats.
necromancer main hand dagger skills do more damage and drain more life.
necromancer death shroud number 2 ability now adds a 3 stack bleed to the target
Mystic Coins can no longer be sold to a merchant
Gathering tools are now available as rewards in personal story
list of trait, achievement and recipice updates
Character creation now kicks you from the server.