I have to say I had a great stay in Vienna and Boris and Andreas have been great hosts! The contact with of them was very friendly and questions were answered promptly.
The appartment was very clean and had all things which are needed for a visit in Vienna. There was a great kitchen and a very nice bath; even dish washer and washing machine were present. The appartment is centrally located in Vienna, there are two major subway lines (U3 and U6) within 5 minutes walking distance. City centre (Hofburg,Stephansplatz) is just a few train stations away, making this apartment a perfect place to stay. The neighbourhood is very quiet, supermarkets are closeby.
All in all I can highly recommend this appartment if you looking for a great central place and really friendly hosts! I would book this place again when I come back to Vienna!