This was our first river cruise and Viking delivers a great experience. The entire staff goes out of their way to make sure your every need is seen to. Our activities director, Clara, was on top of everything at all times and her perky, funny personality really spiced up the experience. My wife and I actually felt sorry for her because the itinerary had to be changed due to a French national holiday which likely created a lot of extra coordination, but mostly because we kept seeing her have to deal with cranky and sometimes rude passengers.
That brings me to the make up of the passengers. This is a couples cruise for the elderly. I would estimate the average age of the passengers was over 70 (some in their 80s). They were probably 99% Americans as well. My wife and I are in our 50s and we were easily the youngest passengers. This wasn't a problem for us and we managed to mingle well with the other passengers but, if you aren't elderly, then you need to understand that a certain amount of patience with cranky people with generally limited mobility on the tours will be necessary.
The food was superb and we both felt we ate too much on the cruise. I especially liked the deserts and the waiters were always willing to bring me two so that I could try more than one. The wait staff, especially Daniel, Marius, and Catalina had great funny personalities and we never wanted for anything. Some other reviews have complained that the dinner process was too long but we never felt that way. As for seating, It is true that some people rush after the evening activities briefing to get their favorite seating in the dining room but we never found it a problem. We sat at different tables the first few evenings meeting new people and eventually a group of us and two other couples eventually all started sitting together and it was a great time each evening sharing what we had seen during the day tours.
The room was nicer than the hotel room we had in Paris. Very nice.