I recommend everybody, who is visiting Vienna, to stop at Nadine's.
We couldn't meet in person but the communication on the web was super easy.
Apartment was really clean and awesome. Also Nadine let us eat some food in kitchen and prepared all stuff for us - like clean towels, instructions and etc.
The apartment is close to the center and the Central Train station (15 min both directions). Give you real feeling of the Vienna.
A lot of restaurants nearby. Also city bike rental system is also near the house.