I loved seeing the castles and wine regions as we sailed through Germany. Stops in small towns with cobblestone streets and gingerbread houses for city walking tours were fun, as was our excursion which included a wine tasting. We tasted authentic German food both on and off the ship, and learned about the country of Germany from expert lecturers.
One aspect that was not ideal were the numerous locks that were required to traverse the river, but we were generally either eating, sleeping, or otherwise occupied, so they didn't slow us down from getting to the cities being visited. It was just not as scenic as having an open river for the majority of the time to view. Also, because it was cooler and more windy than some may have expected in early May, we were unable to sit out on the front deck for lunches or happy hours. We also could not spend time resting on the upper deck due to the weather and the lack of furniture (taken down in order to go safely under several bridges). When we traveled through the middle Rhine where most of the castles were, some passengers braved the cool and wind to sit up on the top deck, but it was not very comfortable.
We had a junior suite which gave us, as two women friends traveling together, a greater amount of privacy. One of us slept in the bedroom and one on the couch in the living area, with a door that closed in-between. We shared the bathroom, of course, but had separate mirrors and prep areas, so were quite comfortable. Our room steward was very attentive and was able to take care of any issues.