Overall I've got to say that I'm really disappointed with Vista. It just feels like XP with a different skin on it and it also sucks up way too much memory - around 600mb idle! The Aero interface is nice, but I wouldn't call it revolutionary.
If you'd like to see a truly revolutionary OS then check out Linux Unbuntu compared to Vista's Aero interface here: http://www.metacafe.com/watch/434675/windows_vista_aero_vs_linux_ubuntu_beryl/
Gaming performance is worse on Vista than XP as well as confirmed by various comparisons on the Net. like this one: http://www.extremetech.com/article2/0,1697,2096940,00.asp
I would imagine that next-gen games will completely own on Vista especially when DX10 cards become mainstream.
As for stability - I've had IE7 crash a few times, as well as other apps from time to time - which is no real difference from my Windows XP experience.