So far, a lot of stuff we already knew. Some other highlights:
FINALLY, GEEZ!"Tooltips in the Auction House will now show an item comparison for a player's currently selected character"
Basically, what WoW has had since Battle.net 2.0, but for some inexplicable reason never showed up for Diablo."Players can now add a note about a friend by right-clicking the name in their Friends List"
Cool. Not something I ever thought about suggesting."Players can now craft items using materials located in the shared stash"
FINALLY, GEEZ!"Salvaged item information will no longer be displayed in the chat log"
FINALLY, GEEZ!"A maximum of eight buffs and debuffs will now be displayed on the UI"
There's a video out already that shows some of the monster density changes http://www.youtube.com/watch?v=2n0a4h0sQ2Q
Also, NV stacks are now multiplicative http://us.battle.net/d3/en/forum/topic/8569328225