The only 3D game I play in Vista is TrackMania Nations, which although it runs a little slower than in XP does run glitch free (well, aside from the glitches caused by a lousy server connection but that's hardly Vista's fault). It does on occasion crash
the GPU driver but so far it's always managed to recover.
I do get music glitches especially during heavy I/O, although not as bad as it used to be. But I do recall reading somewhere that the glitches with Creative's drivers are worse on dual core machines (don't know for certain though).
But overall it's good enough. XP is now only used for one thing on my machine: watching DVDs (because SPDIF still doesn't work in Vista).