As its still beta I dual boot Win 2k with it.
Any advantage, well - Previous to stutter patch I was getting pretty smooth graphice running AH2 under XP64. Prob due to the 64 bit disk transfers.
Disadvantage - As I have an ATI card take a slight frame rate hit, ATI drivers still beta. NVidias have been live for quite some time now.
Was more just to see what it was going to be like. Loads real fast.