Vista is terrible... I'd rather go back to Windows 98 than go to Vista. Microsoft themselves have even subtly admitted that they are pushing work on "Windows 7" because the deployment of Windows Vista has gone so poorly.
Now in reply to the actual topic - I have a friend who has been running XPSP3 for some time and has no problems with it. I however, have not installed it yet. I'll do so though today and post my feedback if you'd like!
Luke