Hi there,
Dan was very flexible about giving me the keys and was very helpful, in general.

The apartment is very basic but nice, and was clean. It is off of the street so one does not hear the traffic and barely hears the tram which has a stop right in front of the door. However, one can hear if some one is staying in the single studio "apartment", next to the "apartment". One can even enjoy (or not) the conversation of the person staying next door. In other words, the walls between the two apartments are paper-thin and it is not enjoyable to stay there when both are occupied:
https://www.airbnb.com/rooms/214707
https://www.airbnb.com/rooms/234613
Therefore, I would not stay here again.
If one ONLY needs a place to shortly sleep, this is ok.
Hope that helps you in finding where you would like to stay in Vienna.
Cheers,
Brian