For me VS2008 was a dog and 2010 flies. I have had plugin perf issues though, but the core IDE has had good perf. At least for WPF and Silverlight apps.
FWIW, I find 2010's performance to be about on par with 2008, not that that's saying much. Since it does more, I'm reasonably happy. Maybe it depends on your video card, or your multicore-ness?