The good: The ship is beautiful. The food was good to very good. The crew was efficient and personable. The itinerary alternated between early days and sleep-in days. There was a good mix of sailing during the day to enjoy the stunning views and sailing at night for efficiency. The heated bathroom floor was really nice. Refrigerator in the cabin. I enjoyed all of the ports.
The bad: The beds were very firm - too firm for me to sleep well. Though it's an option, the French Balcony cabin was not large enough for a twin bed configuration. I don't think the beds were twin sized, they felt like toddler beds. I ended up having to upgrade to my own cabin (luckily available) because the cabin was just too small for my dad and me. There are no tables smaller than six ppl in the dining room. I think Viking needs to provide at least a few two seater tables. The wine included was usually Chardonnay or Merlot and neither were very good. The bathroom nightlight (which can't be turned off) and other power buttons glowed at night which was frustrating. And finally, the ship does not dock in Paris as other cruise lines do.
Viking is a solid choice but I'd also check into other cruise lines if I had to do it over.
Beautiful cabin but not large enough for twin bed configuration.
If this is your first trip to Paris, book time in Paris before or after your cruise or you will be rushed to really see and enjoy it. Book it on your own for a better value (but you lose the transfers by Viking).
The medieval part of Rouen is great but it is small and outside of that area it's a modern city.