I followed the Rhein river from Wiesbaden to Bonn on my European trip and saw some of the docks for the Viking cruise line and a few ships. They have an excellent reputation, the daily shore trips are included in the price as is some beer or wine with dinner I believe. The downside is that they are very expensive at around $300 per person per day compared to around $100 (or less) for an ocean cruise. Cindy has been wanting to go on one but I just do not know if they are worth the extra money. I also question if there is anything that interesting at the places they stop. I saw one stop at a very small town and just had no idea what they were going to see on a tour. They are very upscale but of course the ships are very small. Also be aware that sometimes the river is too high (or low?) and they can't cruise where they are supposed to go. The advantage over a regular tour is that you don't have to spend time every day moving to a new hotel.