We chose the Avalon Waterways version of this Danube River Cruise, because it included a 3-night pre-trip extension in Prague (#1 on my wife's bucket list). We stayed in the Prague Hilton for 3 nights, had several included Local Tours, and thoroughly enjoyed Prague. A barge was stuck in the section of the Danube below Nuremberg, so instead of busing us to Nuremberg to embark on Avalon Vista, they bused us by way of Cesky Krumlov ( a UNESCO World Heritage Site) at their expense. This village was amazing, and probably one of the highlights of the entire trip.
Once we embarked on the Vista, the fun began. Each port included a Local Tour, optional tours, great food and beverages aboard the ship, and entertainment each night. The service was outstanding, our fellow passengers were fun, and the Cruise Director was very organized and responsive. We had Avalon handle the airline tickets (one less detail for us to handle) -- I think we got free airport transfers at the start and finish for them doing this. We saw many really neat old buildings (no wonder they call North America the 'new world'), learned a lot about the history of this region, and truly had a great time.
I rated everything with this cruise as excellent, including dining, activities, service, cabin, entertainment, staff, etc. There were no children on our cruise, and taking children would probably not be appropriate on a river cruise. We really loved this river cruise, and would go with Avalon Waterways again in a heartbeat.
We heard from others that outside balconies on other carriers were not worth giving up 2 feet of cabin space. The French Balcony on Avalon was fine. The bathrooms on Avalon Vista were surprisingly large.