Christoph's place was fantastic for myself and a few friends who were in Vienna for a conference. The apartment appeared exactly as it did in the pictures, and it was comfortable and well equipped for everything we needed (Christoph even left some beer and fruits for our arrival!).
The area was quiet with everything we needed in a short walking distance around the place, plus the city center was only a tram and a u-bahn trip away. We managed to make it back to the apartment at all times of the night without too much hassle.
We couldn't have asked for a better place to stay, i'll definitely keep the apartment in mind if I find myself in Vienna again!