We "sailed" with Viking October 12 through October 19, 2018 with a three-day extension in Prague, starting on October 9. In short, our "Romantic Danube River Cruise" turned into a "Stressful Danube Bus Tour".
Due to low water levels on the Danube, which we now understand has been known by Viking for many months, we were bussed to all our ports, except for Nuremberg (an industrial port with cargo "scenery"), Regensburg and Passau (another industrial port actually located in Sausburg). We never experienced the beautiful river sites of the Wachau Valley, the Danube bend, or Budapest's extraordinary architecture. However, we did experience a boat hotel/restaurant experience on three different ships (not the Var as originally scheduled)--the Tor, the Wilhelm and the Idun--having to unpack and repack our luggage several times and in time for very early bus departures to our next city.
A few of the "highlights" of our bus tour included:
Don't bother getting a balcony as ships dock in tandem and, typically, the only site you will see is another person's cabin in the ship next to you. Cabins were not well vacuumed and maintained.