Just returned from Christmas cruise on the Danube from Nuremberg to Budapest with a 2 day pre-cruise stay in Prague. A fabulous trip. Sightseeing: Daily walking tours with excellent tour guides.....and of course the Christmas markets. A nice mix of scheduled and free time. All the cities were fabulous, but I particularly liked Regensburg and Vienna. I am a cathedral "buff" so really enjoyed the free time we had to explore. Melk Abbey is not to be missed. Also recommend St. Stephan's in Budapest. My favorite though was St. Lorenz in Nuremberg.
AMA staff: The AMA team was very organized, down to the smallest detail. As a solo traveler I really appreciated that. Peter our cruise manager was awesome. The guy could do stand-up. Optional activities: I did a Christmas concert (on my own) in Prague and optioinal tours of Salzburg and Schonbrunn palace. Loved Salzburg. Salzburgers seem to think Americans are enamored with The Sound of Music movie. Many shops played the soundtrack and had SoM souvenirs, which I found humorous. But the city is absolutely beautiful. Schonbrunn was nice but very touristy, even in December. We were prodded along like cattle. Could not take photos inside the palace and the Christmas market was very crowded. Not something I would do again.
Christmas markets: Each market we visited had its own unique flavor. Some items were obviously mass-produced, but it was also possible to find unique and hand-crafted items. The decorations, sounds, and smells were fabulous and just as magical as I hoped. I sampled nearly everything, including the requisite gluwein.