The appartment is really nice. We stayed there 5 days and we could have stayed more time :) It´s clean, you have everything and the location is great! It´s just 5 minutes from Galata tower and really close to many restaurants, bars, little shops... You can get to Sulthanamet really easily by transport transportation.
One negative point, Fatih hasn't been really helpful, first he gave some instructions to meet at a meeting point and then told me to meet directly at the appartment. It´s what we did and then he wasn't really happy because we came directly to the appartment. Also, before coming I asked him by email for some advises of what to do in the area and didn't give me any information.