We booked this trip as it was the first part of a river/ocean joint vacation. The first part was the river cruise from Basel to Amsterdam, we then transferred to the Viking Sky to go from Amsterdam to Barcelona. Both parts of the trip were excellent. Service, food, excursions, everything was well done. There was some concern that we might have to change river boats due to low water levels, but we lucked out. We were told we cleared the river bottom by 6 inches.
Before we left the ocean cruise, we booked another Viking river cruise from St Petersburg to Moscow in fall 2020.
Only possibility of a problem was only a one hour layover in Heathrow. Our flight out of SFO was 30 minutes late leaving. We just made the connection to Basel, but I would never go into Heathrow without at least a 2 hour layover.
There were only 4 cabins left when we booked this trip, so we couldn't get the French Balcony we would have preferred. The cabin itself was fine. The bathroom was small, as on all river cruises, but clean. Cabin itself was also on the small side, but do-able. Biggest drawback was that, being below the water level, the noise from ships passing in the night was loud.