win7 is fantastic for carpc's. the audio stack (which was born in vista), the touchscreen capabilities, and networking alone are worth it- all things that make using a computer MUCH easier then it used to be. too many other reasons to list, but XP is like DOS these days... windows
7 is so much more advanced its sort of funny to me that people still want to keep xp. i dont even run it on my older rigs anymore, i would have to have like a 1ghz / 1gb system to want to run that os... but i realize some people still do (atom processors and such) so for them xp still has its place i guess.