Well for what it's worth, I built myself a new PC back in February and put Vista Home Premium on it, $190 (about 70 pounds), and it worked perfectly. Everything supported fine, all my software runs well, nice and fast, sleeps and suspends properly at last, User Account Control prevents bad software from running un-noticed (basically, it makes you not-an-Administrator unless you answer the 'annoying' prompts 'Allow', so although clicking 'Allow' may seem inconvenient, it saves you having to log off and on as two separate accounts).
There's no way I'd go back to XP, knowing that future software probably won't be supported and the updates will run out some day.
Cheers,
-Alex