Diana was very friendly and helpful with us and it was very easy to communicate with her about check-in / check-out and tourist infos; further pro: it's a very good location near to the city centre.
But honestly, it must be said the apartment actually is a cramped, under-roof (4th floor in an old building, no elevator), very hot room, with just a spare bare mattress with minimal bedding equipment. Even the bathroom had some issues, with few free space and unneffective shower drain, and we had to share it with another guest accomoted in a side smaller room.
In brief, I would really reccomend it only for two people, and just for a brief stop (1 night) in Wien centre...