My wife and I thoroughly enjoyed Viking's Rhine Getaway on the Viking Sun in mid October.
The start wasn't too auspicious because the Rhine was running high and we had to embark from Breisach instead of Basel as expected. Turns out that this was, to me,value added for the cruise because we got to spend extra time there. Although the weather was rainy, the town was delightful. I can highly recommend the Baden wines available in the wine shop on the town square.
Breisach is the stop for the first of the tours offered as part of the cruise. We chose to skip the included Black Forest tour because we expected it to be too commercial based on experience with similar tours in Germany. The optional (extra cost) Colmar tour was the only disappointment among the tours we experienced. The guide was very uninformed abut Alsatian history. The included Strasbourg tour, on the other hand, provided an excellent initiation to Alsatian history and culture.
Cabin 301 is an excellent choice. It is adjacent to the lounge yet very quiet. Also the French Balcony gives excellent viewing while cruising.