General

Map Publishing is now enabled: Using the map editor, you can upload your custom maps to share with the Battle.net community.
Facebook feature is integrated: Here’s a quick way to expand your social network by seeing who among your existing Facebook friends also has a Battle.net account.
3v3 and 4v4 formats are now enabled.
Numerous updates have been made to the Leagues & Ladders system:
Removed Copper League and added Diamond League above Platinum League.
Player ratings start at 0, rather than 1000.
No longer displays loading screen odds in placement or practice league matches.
Matchmaking system logic updated.
UDP is enabled to help improve game performance.
Numerous performance and stability improvements.

Balance Changes

PROTOSS
Sentry
Force Fields can now be destroyed by Massive ground units walking over them.
Void Ray
Range decreased from 7 to 6.
Warp Gate
Subgroup selection priority changed from 2 to 3 so that it takes priority over Gateways when selected.

TERRAN
Marine
Stimpack research cost decreased from 150/150 to 100/100.
Combat Shield research cost decreased from 150/150 to 100/100.

ZERG
Infestor
Infested Terran spell removed.
Frenzy spell added:
Costs 25 energy.
Targets a single biological unit which deals 25% more damage and is immune to snare, stuns, and mind control for 30 seconds.
Overseer
Contaminate spell added:
Costs 75 energy.
Targets a single enemy structure which cannot train units or research upgrades for 30 seconds.
Infested Terran spell added:
Costs 125 energy.
Infested Terrans have the same stats as those previously created by the Infestor and are placed directly under the Overseer when spawned.
Ultralisk
Life decreased from 600 to 450.
Damage changed from 25 to 15 (+25 Armored).
Damage versus structures increased from 60 to 75.

Hotkey Changes (English Only):

Zerg Set Worker Rally Point changed from R to G.
Zerg Spore Crawler changed from W to A to avoid conflict with the Select All Warp Gates hotkey.

Battle.net Interface

Revamped summary pages for player Profiles and Leagues & Ladders.
Added a Help system with tech trees and other tips and tricks.
Removed identifier from the character naming process and added the ability to refer friends for invitation into your party or lobby.
Updated the Battle.net user interface to consistently use a nested menu system.
Added in-game blocking and player muting.

Map Publishing will be awesome, nothing else. With the inclusion of UDP protocols, this seems to be both a double edged sword. This is due to the possible piracy issue with games being played on UDP connectors without being dependent on Battlenet but that is another issue. Facebook...eh. I find it unnecessary to test such a thing like now because its something unessential to the core of Battlenet 2.0 (like chat rooms and other important elements) 3v3 and 4v4 modes now would greatly isolate the good players and the newer players which usually prefer mass 3v3 and 4v4. That means there should be new maps that can support this! The other revamps are fine.

As for the balance changes, Protoss again got another nerf particularly the void ray thats been so dominating for PvT. With forcefields destructible by massive units (Thor or Ultralisk) this will make the Protoss's time harder but not as much since Ultralisk is deemed cost ineffective. We will definitely see more ultralisks in high level play testing. Terran biological army, particularly marines are getting upgrade buffs. Now the core of the latest style of play (Heavy marine usage than previously marauders) are getting a huge buff which allows faster timing pushes and so on. This buff might be excessive for TvZ but better odds for TvP. Zerg got more abilities this time, the Infestor getting an ability to buff unit performance. This will create greater energy tension that already exists between mind control and fungal growth. Corruptor's and Infestor's first spell is now transferred to the overseer, giving it a multitude of capabilities.  We'll definitely see Contaminate sneak attacks. The Infested Terran ability seems to be an energy sink for the overseer considering the stats the unit has isn't very powerful. The Ultralisk has got both a buff and nerf but I consider it generally a buff. The HP reduction to what I see isn't necessary despite force fields do not block it anymore in PvZ but a Terran can still focus fire on the ultralisk. The Ultralisk's role to what I see with the damage change is now a building killer than a tanker. Supply depots and Pylons will fall very quickly, putting good use of the main army while a nydus sneak to snipe such buildings before retreating would be effective.