I'll save the press release copy and paste, but if you want to know at a glance what it does, the feature comparison table
The main new features over the previous are a variation of "content aware fill" as introduced in CS5, but the description sounds like it is a little different but I'm not clear how. Should come in handy regardless.
There's a style match tool... again might be handy to help normalise a set if they weren't shot with that in mind.
Ooh, looks like layer masks might be put back in too, not that I ever learned how to use them.
Maybe not enough for those on 8 to upgrade, but I'm on 7 so I'll get the stuff they added then too. This is on my shopping list. Also enables me to get ACR updates again.