I had one of the few single cabins on the boat and had room to spare. The sliding glass doors, which I had open much of the time, allowed for fresh air and the sound of the water to enter. The bathroom was the roomiest I have ever seen on any ship, close to twice the size of some I have had to squeeze into. The TV and air conditioning were in top shape. The bed was quite comfortable. I did change out the comforter type bed cover for a normal blanket however. I did not discover until day ten that there was an Internet cable connection in the room...I thought it would be wireless and could not sign on...my mistake. Once I plugged in via cable (the ship desk loaned me one) it worked very well and it was fun listening to my Los Angeles classical music station on the Danube, half way round the world.
I never heard a peep from any other passengers, the soundproofing was so good.
There was ample storage for my clothes, etc. and room beneath the bed for my luggage. The staff that maintained the room did a wonderful job, even supplying me with extra bottled water for my CPAP breathing machine that I use at night.
I have been in smaller hotel rooms!