The appartement was wonderful, loyal to the photos. Stefan wasn't there to welcome us, but he arranged that everything works very well and we were received by other people who give us the keys and explain us everything. In the meanwhile Stefan was writing to us the whole time to see if everything was going well.
We really recommend this appartement to everyone. The place is perfect, 1 minute walk to the subway and if you come by car, you can park it two stations away at the P+R, for 3euros a day and buy a subway ticket for the day.
The next time we're going to Vienna, we're definitely staying at Stefan's appartement.

PS: The shower has a radio : it was fantastic :)