Having done three ocean cruises on mid size cruise ships, we wanted to try a small river cruise.
We really enjoyed the ambience and the fact that on a 190 passenger "boat" you get to see everybody and make good friends with a select few.
For me the vessel was the "right size" and well appointed. I certainly did NOT miss the casino, the 'Broadway" type shows, the swimming pools, the Bingo, the constant noise and endless children running al over the ship.... The one and only think I would have enjoyed would have been a Sauna and or Steam bath which I personally enjoy and I think fits in very well with the Viking/Scandinavian roots that you so well represent.
Average size but well appointed. My favorite thing was the heated floor in the shower and bathroom.