According to the now ending poll over at cyberD, XP is still the greatest, it wins with a whooping 83% of all total votes. :)

Aprox 230 votes counted this month.

As for my own personal opinion, I'd say the same. Vista is according to among many the biggest large product failure since the turn of the millenniums. Seven seems to be a much better choice however, with support for old OS applications (Vista didn't have that, very bad), built in firewall and anti-virus and a much lighter explorer than the latter release. Graphically not much has changed, though.