Vista can run pretty decent with the right resources like a dual core cpu and arround 2 GB RAM and at least an 8 MB cache HDD recomended will be a 16 MB cahce thow, but the compatibillty with emulation isnt that great as with XP (i'm suprised nobody said anything about this
after all this is a emulation site
) ) So with vista its all about computer specs and what you will be using it for. As for DirectX 10 it all depends on the game, but in theory yes directX 10 is a big improvement when it comes to graphics and no there is no DirectX 10 for XP yet apart from some beta DLL's moded by some guy i forgot he's name
AND NOW ABOUT LINUX: ALL linux distros are meant for Desktops its just that you have alot of work to do on them alot of configuring but there alot more cooler with the eye candy than any version of Windows. I tried linux a few times and from my personal experience i can say it rulles when it comes to eye candy