As a regular ocean cruiser, first time river cruiser, I found that my river cruise* on Viking was more like an ocean cruise than I expected. The free beer and wine with dinner and included shore excursions were a nice change, though. This river cruise was also more like a bus tour than I expected.
There is an optimal experience that the ads portray...eating, drinking, and laughing with other passengers, outdoors with blue skies, and beautiful scenery floating-by. Of the six days and 20 hours from bonjour to au revior, about 20% of the cruising was when we were aboard** and it was not during sleeping hours. But about half of that was spent either waiting in front of a lock, or in the lock. The first time, the lock is cool, but it's preventing the optimal experience, especially since it looks like it's midnight and there's a slimy concrete wall an inch from your nose. So an average of 2.7 non-lock cruising hours per day. Although the rivers were low at the time, the top deck was often closed for bridge clearance, so having the optimal experience was limited to the bow, which held about 40 people (out of the 180 on board). Not that you couldn't enjoy the view from your stateroom, but not enjoying the view with other passengers. So if you were on-board, it wasn't raining, you found a spot outside with likable acquaintances, there's something besides the inside of a lock to see, well, you get the idea. I think this happened once for me. I predicted this would be the case, but make sure you have your expectations set appropriately.
I've only been on one bus tour in my life, and that was with a single bus and 35 other students (a long time ago). Sometimes our ship would be parked where we could walk to the city/town. Often we were out of town, so boarded four huge coaches. Either way, I found myself walking around a couple of city blocks or a tourist venue with a gaggle of 180 other passengers. At times I was engaged with what I was seeing, but other times, I just wanted to be away from the crowd. If you wanted to see these same sites, you could drive from start to finish in a rental car in 4 hours. So a few strategically place hotels would mean you'd only need to move once or twice and do day trips to the sights. If you really wanted to see the city from the river, you could book a afternoon or evening cruises. And if you did it with a car, not only could you be away from the gaggle of other passengers, but also wouldn't be tied to the river geography. Again, if you expect to be with a big group, and don't mind that, then having a turn-key vacation where Viking does all the planning might be a great way for you to see the sights.
Very tight, but efficient. Very similar to a modern ocean liner room.