Great apartment, very (VERY) well located in the center of Vienna. Just about 4-5 minutes away from the Stephansdom. Difficult to be more central than this!
The apartment looked exactly how it was described on the website. We were a group of 6 and the 2 bedrooms + the sofa bed in the main room were perfectly fine for us.
Andreas was very welcoming in his emails before we got there, and the girl welcoming us in person was 1) perfectly on time for the meeting, and 2) giving us some useful tips for the apartment and the city center.
I'd warmly recommend this choice for any stay in Vienna!