Shitty 7 and Vista. Just because it's Dx11, had bad experience with them
Not many say that any longer. I am one of the worst Microsoft bashers around. However, I beta tested Win 2000 (started as NT5), XP, Vista, 7, WHS v1, WHS v2, Server 2003, and Server 2008. Mostly to learn, but also to make each product better because the IT community and users would have to live with the products.
That being said. Win 7 is, by far, the best of the bunch. Vista's reputation was so tarnished by bad press, and not necessarily bad tech, that it could overcome it.
XP is dying in terms of MS support. Win 7 is the way to go. However, if you need help with specific areas of support with Win 7, you are definitely at the right place (Tom's) to get help.