We chose the Viking Egil Romantic Danube as a last minute adventure, and were pleasantly surprised that rooms were available three weeks before sailing. Viking travel did an excellent job of arranging discounted flights and transportation to/from the ship.
We cruised (below the water line). We found the room to be comfortable, well laid out with large window near the ceiling that provided a view of the river and passing boats, etc. We spent very little time in our rooms so the lack of a balcony wasn't an issue. Our room was very quiet. You could hear a little water noise but nothing that would keep anyone awake. In most ports our ship was one of many in port so the view outside our room was another ship. I'm glad we didn't opt for a more expensive cabin.
Our cabin steward was excellent. She kept the room clean, and was able to handle a few special requests with ease. We were especially pleased when the hotel manager was able to rescue us after returning from an adventure in Vienna where our sneakers were soaked (the water was several inches deep outside the subway station). The crew was able to dry our sneakers over night so we could continue our adventure in the morning. I can't say enough about how everyone in the crew went above and beyond to make our cruise a special occasion.
We cruised in a category E cabin (lower level mid-ship). Our room was in excellent condition, quiet, and had plenty of US and European outlets. The climate control worked well. There are also outlets on either side of the bed to charge your phone or power medical equipment.
The only problem we encountered was burned out closet light. Viking corrected the problem within 10 minutes.
We were very pleased with the room, and staff.
One really nice feature of category E rooms is that the exterior wall of the ship is quite wide near the base of the window. We used this shelf for storage or as a drying rack. Just be ware that another Viking ship will likely pull up next to your window so your items will be on display.