I stayed 4 months in Kilian's apartment and would definitely go back again if I end up spending longer periods in Vienna in the future. It is bright and spacious, overlooking a green inner garden, as well as a quiet street. I am very sensitive about ambient noise, but I was not disturbed here at all during work or rest. The area is not too touristy, which is a big plus for me. Yet, it is conveniently close to excellent public transportation service (U6 and trams) and there are several shops and restaurants within minutes' walk too. I bike a lot and the proximity of the Vienna Woods was also quite attractive for me. The neighborhood seems quite safe even when walking at night.
Kilian was very responsive to any requests (one or two small things had to be sorted out when I moved in) and tried to be as helpful as possible. On the other hand, he is not an intrusive host at all, so you can really feel at home in this apartment.
Thanks, Kilian! I hope to be back some day.