We had an excellent stay at this apartment, the location is great: transportation very close by and excellent neighborhood. The apartment (and building) is really quiet and one can really relax after a tiring day. Everything was nicely set up and perfectly clean for us. It was good for three people, but could accommodate four, too, in my opinion. There are supermarkets at a very close distance and it is a walking distance from the ring. Kitchen was also well equipped, but since we were out a lot we barely used it.
Only issue was the wireless internet would just stop functioning for no reason, sometimes for the entire night, but we didn't really need it being out all day and relaxing during the night. If you have trouble with stairs just make note that the apartment is on a 3rd floor.
Communication with the host is really quick and everything was explained very clearly from the beginning. Would love to stay here again, next time I am in Vienna. :)