Been using x64 Vista for over a year. It came with the laptop and it works just fine. The other laptop has a 32bit verion of Vista and love that too.
Once I used vista I never wanted to go back to XP. XP started to look archaic suddenly.
Once I can get my hands on a legit copy of win7 I will upgrade and probably never look back . Thats the thing about Windows operating systems - you cant stick to one for too long and the next one is always better than the one before. The only exception to that was Windows ME ( millenium)...lol