If any of you guys go to Hungary, the Statue Park (
www.szoborpark.hu) is a must. It is just outside of Budapest, a fun collection of communist memorabilia, especially the big, classic outdoor statues.
Lake Balaton can be overcrowded, yes, and just try to avoid being ripped off (this might happen in many places in the region if you are from the West). You don't have to go to Szeged to get a good gulyas, just don't go to any fancy restaurant. "Bagolyvar" a mid-range restaurant by the Budapest Zoo is a good place to eat. The Hungarian kitchen is great (unhealthy as well, but only if you live there long enough), the fish soup, the chicken paprikas and the gulyas being especially famous.
And yes, Vienna is a must, and make sure to get to Krakow (I like it better than Prague, it's more authentic). Not very far from Krakow I hope the salt mine of Wieliczka (sp?) is still open. That's cool, if you haven't been in a salt mine before.