I haven't been to Krakow - but have heard it said that it's "pretty, but overrated".
I've never heard anyone say that people in Vienna are cold - certainly not my experience.
Unless you're planning to be in that part of the world soon I would include Budapest - definitely a place worth seeing. (I've been there twice, once last year and once on a back-packing trip in the old Communist days back in 1978... needless to say it was quite a different place back then!)