im leaning towards putting winxp pro on my new htpc
Vista's fundamentally flawed (just google the issues people are having with it) - New version of Windows should be available by the end of next year (2009).IMHO EVR looks way better than VMR9, sticking with XP is sticking with the past, MP must move forward with OS changes or it will eventually be left behind.
XP - rock solid stable and fast
I use Vista at work on a few different machines and have different issues with each. (outside of MP of course)