I've generally been happy with purevideo in general, but it's a pain to get to work just right, and nvidia's hit and miss support for accelerated video as opposed to gaming improvements has driven me crazy. Sometimes features stay working in a new release, and sometimes the break stuff that used to work.
Now this - I have to wait till June for XP support? It's enough to make you switch to ATI. What kind of nonsense is this? Nvidia isn't exactly a small company. They can't do parallel releases of Vista (which no one in their right mind would use if they care about stability), and XP? What's the deal nvidia? Why don't you switch to folgers in the cafeteria and use the saved money to make stable HTPC drivers that just work consistently for both vista and XP!