Krakow is definitely worth seeing, yes. And the trip to Auschwitz also. Make sure to plan a whole day for it and make sure to go to Birkenau as well (the destruction camp, largely destroyed, but walking through that huge area with your memory working and your imagination bringing up all the terrible stuff you know about what happened there - that's one of the worst and most intense experiences I've had so far)... some of the exhibitions and brouha in Auschwitz (the work camp) is high-gloss crap, but it's definitely worth looking at some of the pavillions (when I was there, about ten years ago, each nation had their own pavillion with their own "history" and exhibition in it - guess that's still the same - and the jewish/Israeli one was just loads of images trying to impress, but others - mainly the Polish - were very good.