I stayed at Fatih's flat for 2 nights, as I was in transit back to Canada with my friend. It's a very good location--Istiklal and the Galata bridge are only a few minutes away in either direction--but be ready for the very long flight up the winding stairs if you have a lot of luggage! Also, while the Galata area is convenient, be prepared for steep hills and confusing streets. The property itself is wonderful for a short stay--clean and functional. The bathroom is decent and there's a comfortable bed. The windows are large and it faces the water so AC isn't really necessary. I didn't do much cooking so I can't say much for the kitchen--there are a decent amount of pots, pans and dishes.
Fatih himself is very nice and welcoming. We came so late, but he was available to speak with our taxi driver and picked us up. He stayed with us if only to help us plan our trips and give us 'insider tips' on the best places to get baklava, food etc.
I have no complaints, really. So if it's your first time coming to Istanbul this would be a wonderful place to start!