This was our very first experience with a river cruise. We selected Ama based on recommendations both from our travel agent and friends. It was an excellent choice and there's really very little in the way of anything negative to say about the cruise or the cruise line.
In terms of the positives, the ship was excellent. It was very well taken care of and well maintained by the crew. The cabins were very nicely appointed, and assuming you pick the right class of cabin, much more room than you might expect on such a small ship (more about that later). The food was just superb... very well done with lots of choice and really something available to eat virtually any time during the day if you're feeling a bit peckish. The specialty dining venue is called the Chef's Table and it truly is something special. You're entitled to eat there once during your cruise (no additional charge) and it's very much a "don't miss" affair. The crew was very attentive and willing to accommodate most any request with a smile.
On the negative side, not having done a river cruise before, I think we chose not so well in terms of the cabin that we selected (French Balcony). It was certainly comfortable and quiet, however, the size was fairly restricted. The bed took up the majority of the space in the cabin and in fact trying to walk around the bed often required having to move the desk chair to a different location. If it's affordable, I would definitely recommend at least the next cabin class up where the cabin size and layout seems much more practical.
Unless you are really trying to save some money and are not concerned about a very small cabin, I'd recommend going the next size up. The bathroom was fine and well outfitted. The room was cramped and navigating around, particularly with two people, was very awkward at times.