We went to Heidelberg, the Dolomites (incl Bolzano), Venice, Bavaria (for my grandfather plus Rothenburg and Nuremberg), Berlin, and Mainz. We attempted Verona but had problems with Christmas crowds going to the market at the Arena. We returned Wednesday but are having jet-lag problems (very little problems going over.) It was my family's first trip to Europe- I used to live in Germany and have visited other European countries, but I haven't been overseas in 16 years and never without my parents.
Loved the Dolomites (my third visit), have mixed feelings on Venice, Bavaria is great, Berlin is so worth a visit, and Mainz and Heidelberg are so much better than Rick gives them credit for. I did a LOT of planning and research, and it was worth it. Still had a few directional problems from time to time and I left my pricey country maps and my Italian and German phrase books (ok without German, it came back for me, but I was useless in Italian) at home. We did have the GPS, though, but with snow, tunnels, and mountains, we lost the signal a few times when it was needed.
I am already planning my next trip, although I wasn't planning on THAT, again, already. ; ) I am trying to get my parents to go with me (my husband is not a good int'l traveler, we found, and my autistic son would rather stay home) and my girls and stay in Bavaria the whole time near family and just venture from there. We are glad we saw what we did and stayed most places 2-4 nights, but I'd rather have one home base next time.