Have gotten a lot of helpful info from you all so wanted to reciprocate. Just returned from Krakow and Prague with a stop in Warsaw (used a FF tkt so did Warsaw as he stopover from Prague/DC in order to go to Krakow.)
Warsaw was interesting and it was fascinating t see how well they had rebuilt the old town, destroyed in WWII. We stayed at the Meridien Bristol and it was lovely.
Krakow is a terrific and very beautiful since it was spared during the war. Costs are very low, people are extremely friendly and you can by with English (I had a Polish dictionary and people really appreciated it if you made an effort to try some words, especially a thank you or goodbye). In Krakow, stayed at Globtrotter for about 30e for a single room that was more than adequate. TV, shower, plain decor but fine and a very helpful, friendly group at the front desk. Good location that was easy walk from center of town. Cheap eating in Krakow---enjoyed a terrific veal goulash at a Hungarian restaurant (Balaban, I think---the only Hungarian one in town) on a posh street running from Wawel Castel to the old town. The castle was beautiful and well worth visiting. Krakow is small enough in scale to get around very easily. Not a lot of English or American tourists and it didn't have the packed feeling we had later in Prague. A magnificent town square lined with cafes and filled with people, especially in the evenings---a fun souvenir market also in the center of the square area. Also had a very good meal at Chlopskie Jado (think that's the spelling) Great walking town---lots of amber, wood carved folk crafts, etc. With cheap flights now from London, things will start to change----go soon!
Visited Aushwitz---a must do.
We took the train from Warsaw/Krakow/Warsaw. Next time I would fly from Krakow directly to Prague---we didn't because of our FF routing. The train was fine though and seeing the Polish countryside was interesting(very flat around Warsaw, much hillier around Krakow).
Prague is probably the most beautiful city I have been in, including Paris and the other European cities of note. Each turn produces a jaw dropping architectural gem. We stayed at Hotel Salvator. Unless you are a very sound sleeper, do not stay there. Yes, a value for the price---nice room, very clean, decent breakfast, easy Internet access.....BUT, a courtyard that houses a charming restaurant where people sit until midnight and the sounds travel easily to your room! Construction now means the other side of the building is also noisy. Very good location so I'd maybe try them again when the windows are closed and people have to eat inside the restaurant! Prague is not cheap but well worth every penny! Food is more expensive than Krakow but not Paris prices. Had good pizza and salad at a Kampa Park sister restaurant right on the Mala Stran side of the Charles Bridge (can't remember name). The French bakery Gourmand Au Gourmand is as good as any I have been to anywhere in France. Chez Marcel is a good, reasonable choice for French food, not fancy, reasonable, feels authentic. We saw 2 operas at the spectacular opera house---go no matter what is there! And, thanks to the Fodor talk site and book, we went on the tour of the Odeci Dum (Municipal House)---an absolute must do!!! The performance venues in Prague are awesome. We enjoyed a day trip to Kutna Hora (didn't have time for Cesky Krumlov)---reasonable cost and nice to be out in the country.
Prague is teeming with American/British/German tourists. I can't imagine what it is like in peak summer season. You can hardly cross the Charles Bridge now!!
Did all the standard tourists stuff---Prague Castle,the Bridge, Josefov (old Jewish section), the astronomical clock, old town square) Make sure and do the Venice-Prague 45 minute boat tour----can take it on either side of the Charles Bridge and is a delightful experience.
I am currently experiencing Czech beer withdrawal........If I can be helpful with anything else in trip planning to these towns, let me know!