As part of an eastern European trip, I plan 3 full days in Warsaw, a day to get into Krakow with another 3 full days there including a trip to Auschwitz. Too many nights or about right? I've been told there is much to do and see in both cities.

This sounds good. Don't mean to slight Warsaw, but I might be tempted to do two full days there and give Krakow four full days. I loved Krakow, so that is just my bias.

We did 2 days in Warsaw, took the train to Krakow for 3 days and returned to Warsaw for 1 day. We wished we had the extra day in Krakow.
On saying that, I enjoyed the Warsaw restaurant food better than Krakows.

Polite suggestion. Define your interests. Warszawa and Krakow require a hundred lifetimes to explore...Sports, food, history - no end to it, schools, museums, theater. For instance: Polish medicine is now at the cutting edge, are you medical people? Advertising...state of the art. Music...try chasing Chopin...The NE is still one of the great nature parks left in this world. Military..Try cemetaries. Ancestor research?

All suggestions appreciated! Looks as if we'll spend about 2 1/2 days in Warsaw and 3 1/2 in Krakow. Thanks!

Note...Eastern Europe begins in Moscow, Berlin to Moscow is central Europe.