I love CroisiEurope river cruises, but they are not to everyone's taste. The main language on board is French. You'll find there are few English speaking guests. Excursions aren't included in the price (except for cruises sold in the US where the prices are higher to take that into account). Cabins are small and the shower room is tiny. If you want to be cocooned in your own little piece of England (or America) and don't speak any other languages, you need a different cruise line.
We went on Victor Hugo for a trans-Europe cruise from Strasbourg to Budapest. This is really a repositioning trip to get the ship to Budapest for the summer season, but it's a great way to visit 5 countries.
We're not great fans of organised excursions. We prefer to disembark on our own, see any major attractions on the way and have coffee with the locals. That makes CroisiEurope cheap. One point to note is that with a repositioning trip, the ship needs to get through the Main Danube canal as quickly as possible, so some excursions are dropped off at one port and picked up further along, leaving no opportunity for others to disembark. That's not a problem if you enjoy sitting on deck watching the world go by. There are only so many pretty German towns you can take in on one trip!