The Viking Sun was seven week old when we boarded -- gorgeous! Some rough spots with a new ship, but minimal and resolved. But the itinerary was lacking --- way too much time on buses (nice as they were, with great tour guides). If the ship was too large to go into to the shallow Havana harbor, why not stay outside the harbor and use the tenders since it had to use these in Cienfuegos anyway?
Overall food and service were good, but service was much better for dinner when 300 people were still off-ship on excursions. We were disappointed in the Italian speciality restaurant -- menu was plastic, crowded tables; service and food were OK, but not special. The Captial Table speciality restaurant was excellent -- interesting fixed menu, with supurb service.
We heartily recommend the Viking Sun, but not the itinerary if only one port in Cuba.
We were disappoinnted in the size of the cabin. Having traveled on several Viking river cruises, we were surprised at the confines of the cabin on the Viking Sun. Friends in a "penthouse" cabin had sufficient room that we did not have.
Entertainment was good for a medium sized ship -- much better than the Viking River Cruises, but not at the level of larger ships.
Probalby a nice city to visit based upon the comments of others, but we only rode through it as part of excursions to other places. Would have liked at least a half day to explore the city.