As bigbuy said, Budapest is very classy, and plenty of spots to have fun. People (at least young) are usually laid back and relaxed.

Warsaw lacks on the sightseeing part, some would call it grey and Polish people are in general more reserved (although I met some great exceptions!), and service is sometimes lacking. As someone posted on the InterContinental Hotels Group forum: http://wumocomicstrip.com/img/strip/...2009-09-15.gif

Bucharest combines the worst of the other two cities, and then some