I just returned from a Viking River Christmas market Cruise (December 20-28). Here's a short summary:
The Viking crew was wonderful. They were very accomodating and helped whenever they could. The food was great and plentiful. There were no low water problems and the trip went as scheduled.
The Viking reservations people in the states were completely incompetent. They fouled up our reservations and forgot to include one of our flight coupons. Then they claimed that it was our fault because we didn't check the documents thoroughly enough. Several other mistakes were made in spite of our efforts to watch everything.
There was sickness on the ship. About 40% of the passengers caught the "flu" for at least one day. A few were sown for more than that. The crew was helpful but there was little that they could do.