The duration and locations, especially starting on the Black Sea. Very happy we went from east to west as it consistently got better all the way to Prague. Budapest and Prague were great large cities and the smaller towns like Durnstein and Pecs were great surprises. The Passion was very nice with a small spa, but the exercise room was way too small. I couldn't lift the weights up as they hit the ceiling and the max weight was 10k. Matre'd was very accommodating to my wife's pepper allergies and there were some vegetables at the breakfast buffet for me. The tours of the towns and cities were well done, although most of the guides have their speech idocincracies. The presence of the Habsburg family made it a special themed cruise and more personal (only the portion from Budapest to Regensburg). By the end, we had heard the stories repeated so many times about Sissy, that we didn't want to hear anymore. Would have liked to have been involved with more sustainable activities and performances, like our Avalon cruise on the Mekong.