OK, I'm back.
AaronP, you seem to be giving contradictory advice. I've had a reply from AdamK over at Compiz. Here's the thread:
He picks out posts by you stating that it's an X limitation, not a Compiz bug - Compiz can't possibly perform the VBlank in this situation. So you've suggested an upgrade to X to improve the situation:
So who should I be hassling to get this fixed, or offering my money / testing services towards? Nvidia? X? Compiz?