I don't think I made myself clear in my first post. Our plan is to fly to Italy for a wedding in Florence. We have accomodations for 6 days there and planned to do day trips. We have another 8 days to go up to Eastern Europe and we hoped to do Budapest, possibly Vienna and Bratislava is in-between. Or do you recommend just staying in Budapest the next 8 days?
Go for all 3 - 8 days should give you time to sample all 3 cities.
I'd split the time between Vienna and Budapest, both of which are easily worth four days. I didn't think much of Bratislava.
I thought Bratislava was interesting but didn't warrant more than a day. It can easily be done as a day trip from Vienna, when I went the ride was about an hour long and the trains ran appx every hour.
I spent 3.5 days in Budapest, and probably could've done with another day at least. It's a wonderful, interesting city.