First, the ship: Brand spanking new and it showed. Everything was meticulously clean and polished and the size of the ship was perfect. The "verandah" cabin is also perfect with the roll down window. The staff was superb throughout.
Second, fellow passengers: Having only 120 or so on board for 2 weeks meant we were able to get to know many and make some good friends along the way.
Third, the rivers (Rhine, Main & Danube): All are gorgeous with boundless curves, hills, castles and cute little towns and a couple of big cities.
Cabin is very comfortable (for a ship!) with very comfortable bed, smallish bathroom (expected) and a huge window wall.