The location of Hasan's apartment is perfect -- in a very non-touristy but foreigner friendly neighborhood, close to cafes and supermarkets and just a short walk to public transport. Although within proximity to the busy Taksim and Karaköy/Galata areas, the neighborhood is quiet, calm, and feels very safe.
The apartment itself is on the small side, and cooking is limited to an electric hot plate, but it is clean and comfortable nonetheless.
Hasan was extremely responsive the entire time, flexible with check-in, check-out, and luggage storage, and really made an effort to ensure a positive, comfortable stay.