Although our river cruise did not start off on a positive note because of low water levels and we had to change boats twice, I found Viking to be very efficient in ensuring that everything went smoothly.
Stay on both Viking boats (Atla & Jarl) were enjoyable; both cabin rooms were comfortable; both staff were friendly and helpful; food was a bit on the salty side on Atla though; tour guides were excellent and provided detailed history of many of the cities; loved the headsets which allowed you to hear the guide even if you wanted to 'wander' a bit; relaxed and casual dining atmosphere.
Onboard 'entertainment' did not interest us too much, but we were comfortable with retiring to our cabin to watch TV.
We thought it was worth the extra money to upgrade to a room with a view. It is an advantage to be able to pull back the curtain for a panoramic view of the scenery and also nice to open the door for some fresh air. The cabin was well laid out and extremely usable. The bathroom was clean and spacious enough. There was little noise at any time (from the hallway/adjoining rooms or plumbing) and the ship made virtually no vibrations or mechanical noise. No problems with wifi connections. TV provided enough movie entertainment as well as weather/tour information.