Mustafa and his partners were very kind and helpful with our stay. They allowed us to check in at around 1pm on the day of our arrival and offered us maps and tips about seeing the area. One of the hosts, a woman whose name I unfortunately didn't catch, was especially nice and helpful -- for example, she told us (two girls) the safest street to walk down when returning to the apartment at night, and when we checked out the next day she even gave us a little parting gift!
The apartment was pretty small but clean and nice, although it had a bit of an odd smell when first walking in. The building had construction going on on the outside of the building, so there were a fair number of loud noises during the night and early morning. The location of the apartment was great -- only about a five minute walk to Taksim square, nearby some cute-looking cafes and restaurants, and about a five minute walk from the Havatas bus stop to take you to Ataturk Airport. Overall, we enjoyed our stay here and would recommend it to others.