Been running Vista 64 Ultimate for about a month now and its solidified my current rig as the relatively highest performing, most stable, and problem-free rig I've ever built. I didn't have any real competitive options when I built my rig in January, but other than my original mobo I've had no regrets about any of the components I picked.
Nvidia had some general problems and game compatibility issues early on but the drivers have been very good with regular updates and improvements since March. I think my machine has locked up or rebooted on its own 2x since I installed Vista (yes, uptimes of weeks at a time, amazing) and one of them was for an update. I had similar experiences with XP as well, as I was able to complete entire runs in Titan Quest in the same instance of the game by simply alt-tabbing out whenever I wasn't playing.
There were some serious problems with LOTRO and Vista, with many of the problems N7 describes, but it was clearly an LOTRO client problem and not a Vista/Nvidia problem. The last update fixed the Vista CTD and driver restarting problems entirely. Vista also seems more picky in terms of RAM timings and read/write fault tolerance, as some early problems I was experiencing in Vista once again pointed to faulty RAM (and most likely, a faulty motherboard). Swapped out the motherboard and RMA'd the RAM and its been smooth sailing since.
One main complaint about Vista is that is slower than XP, with only 2GB at least. Alt-tabbing between games and apps, particularly in games with large textures takes way too long. HDD thrashes a lot and performance is generally slow. My other 2 GB of RAM gets back in from RMA today so hopefully that clears up the sluggishness.
Overall I'm very pleased with performance in Vista, although I haven't bothered to re-install some games. I've installed and played enough of them without problems though, so I'm leaning towards game-specific problems rather than any endemic issues with NV/Vista drivers. Creative drivers are a different story though, so I guess that'd be my other main complaint.