We took a fourteen day river cruise on the Viking Idun. This is a new ship with several problems. For one our shower drain did not work properly and flooded our cabin once and our bathroom the second time. There is a leak in the lounge that causes the entrance way on both sides to be constantly saturated. It smells, and has been like this since almost the initial sailing. Several days there was a terrible sewage smell on the lower deck, sporadic problems with toilets.
The concept of river cruising is not for all. The days are long with hours of nothing to do. For some this is wonderful, not for us. There is no spa, casino, gym, art auction, etc. this is very laid back. You sit and watch the castles go by. Meals are at a set time, no room service. Being used to large ocean liner cruisers this was difficult for us. Since you sail through many locks that are low to the ship there are many days where you can't sit up top.
There are things that Viking does very well. Having a leisure tour group for those who need a slower tour group, quiet boxes on the tours, so you can hear your guide without standing on top of him or her, good food, pleasant staff, and water available at each port.