I've had two problems: crackling audio and NVIDIA's driver coming up with strange errors.
the former was fixed by buying a cheap PCI-E soundcard and passing it through (line-in'ed to the primary soundcard), and the latter by twiddling some QEMU flags, as NVIDIA want you to buy the $4000 quadro... my next card will be AMD, who don't do this sort of BS.
now it's all sorted it works like a dream, you wouldn't know it's in a VM.
