We just returned from Uniworld's 15 night Istanbul to Vienna with a Prague ad on. It was so totally different from an ocean cruise. The first 3 days were not what I expected, long bus rides to the towns and a day in the Iron Gates with not much to do on board.
The cabins are very small, not enough room to pass each other around the bed! Also, the French Balcony was wasted when we were tied ...