Very good location, and clean and nice apartment - that's what I would like to say after staying here. All of this after saying that Mehmet is very good, hospitable, friendly host, who really cares about his guests.
I would recommend to choose this apartment if you're going to Istanbul - it will definitely make your trip better :)
Here's more details:
Apartment is located very close to the center of Istanbul, which is pretty crowded, but still I never saw any "side effects" because of that. So its easy for you to take a ride to some place as well as find any market you want, take a walk or find a place to eat - cozy restaurant, some authentic cafe or just fast food place - it's all there. If you're interested in bars or clubs - it's all there as well.
If it might make you think there might be dangerous during night time - I would assure you that I never felt it there even during the night on small streets :)
Mehmet always was nearby when I needed help, he helped to enable heating system (I was staying when it gets colder during the night), allowed to drop my luggage before check-in time and allowed me to stay a bit longer when I had problems to pack my bags. Also he was always in touch in messenger so it was easy to communicate.