I haven't tried the full release quite yet but I tried the Ultimate version in Beta. The only awesome feature I can say I truly noticed loved is that I liked the profiling systems which I never had in 2008 pro, but 2010 pro won't have them anyway as far as I understand, so meh.
A huge improvement I DID notice was that WPF didn't crash in designer mode all the time which I've had a lot of problems with in 2008.
On the downside, I do feel it's a bit slower.
Honestly I'll probably upgrade for my personal projects, but anything I'll be working with a team on I'll still be using 2008 due to the fact that not everybody will have 2010.