We stayed at Cristoph's apartment for 5 days.
He was extremely hospitable, very organized and easy to reach, and all the information we could need (local transportation, shops etc.).
The apartment is located in district 11, but easy transportation to anywhere you need in Vienna. To those who are poker fans a big poker room is about 7-8 minutes walk away.
The apartment is very nice - clean, spacious, comfortable with a double bedroom (2 single beds) and a big living room with a couch fit for a 3rd person if needed.
We enjoyed the apartment very much and would definitely book again next time in Vienna, highly recommended!