adventure 22 days in Eastern Europe

22 days/ 6 countries = less than 4 days in each country and that doesn't even include travel time between them. Without knowing any details, it sounds really ambitious and you'll get very thin coverage of each country that way. If you want to get helpful advice, you need to drill down to the city level and figure out distances between them first before you can string together an itinerary. Since you didn't name any cities and kept your question at a very high level, no one can reliably tell you best transportation options.

in 2011, we did Vienna (4 days), Budapest (4 days), Plitvice Lakes (1 day), Split (2 days), Ljubljana (1 day), and Austrian countryside (2 days). That's half your list. It was a big circle, so we never backtracked, and flew in and out of Vienna. But we didn't spend enough time in Slovenia, Hungarian countryside, or Austrian cities. I would chose either Northern (Czech Republic, Slovakia, Poland) or Southern (Austria, Hungary, Croatia, Slovenia). If you have never gone to these countries, it not important which you choose, but you need to choose. The original list of 7 is too many. With a tour, maybe, since the tour guides do the details of where to stay, etc. But on your own, you must choose more carefully.

So much land to cover, why not take Rick Steve's 16 day Eastern Europe trip. We just returned and it is fantastic. We usually travel independently using his guidebooks, but felt we couldn't cover all of these countries without wasting time and money. Add on Austria at the end of this tour.

Hungary, Slovakia and Austria can be made into a pretty efficient two week trip and three would not be too much. Next I would add the Czech Rep to the tour if you wanted but I would stop there. The logistics to add Poland or Croatia for my taste are too much in the time you have. I would start in Prague for the longer trip or Vienna for the shorter trip and depart out of Budapest in both versions of the trip. Either way most of the travel can be accomplished by train in 4 hour or less legs.

I am a bit crazy when it comes to travelling...I think everything is possible or almost.
It depends what type of experience you want! It is your vacation! :)
I just returned from a 2 week trip to Norway, Finland, Denmark, Czech Republic, Slovakia and Latvia.

Of course you can probably see just one or 2 cities per country if you go with your plan A....are you OK with this?

If you want to squeeze in Slovakia and just get a preview of it...Perhaps you can try what I did...
I took the earliest bus out of Prague and came back the same night (left at 7am and came back at 11pm). I felt I got a good overview of Bratislava by walking and sightseeings the city for about 7hours.
(You could take the same bus to Budapest too....I recommend Student Agency. Super bus! Free wifi, free coffee, restrooms, free movies, etc)

I'd probably save Croatia for another time...It is beautiful all year long...but very nice in the summer to enjoy the ocean. And it is a bit further than other countries you have mentioned.

Have a wonderful trip!!! :)

I am afraid that Jackie is already back from her trip (October?).