We spent 5 nights at Stefan's apartment and I'd recommend it with no doubt.
The apartment is very clean, well located and cosy. There are supermarkets and restaurants nearby. You can get the city centre by using the U-Bahn (Thaliastrasse, 10-15 min from the house) or the S-Bahn (Schottenfeldgasse, 3-4 mins far away from the house).
The apartment has everything we needed for our stay in Wien. Also, the communication with Stefan for the check-in and check-out was easy.