We didn't meet Stjepan, as he was busy, but his wife Dajana was very nice and welcoming. The flat is good for two people and cover the basic needs. The flat was located in a quiet area 2 tram stations away from Praterstern, which is connected to other tubes going into the city center. We didn't have much time to explore the surrounding area, so we didn't see a supermarket or tested the restaurants nearby.
In general the stay was very pleasant and I would recommend Stjepan's flat to everyone coming to Vienna :-).