I stayed there for a week and was generally happy with the flat. It is well situated in a very quiet and safe part of town, there are many shops and restaurants nearby and it is very easy to reach from the airport by bus. All the famous parts of Istanbul are within walking distance from there. The flat is spacious and generally equipped with everything you may need (there was definitely enough towels and the bed wasn't broken, despite what another user said). The host was very friendly and flexible and I had no trouble whatsoever during my stay. Plus, the flat has a nice terrace with plants where local cats come to nap on the bench.
The only thing I didn't like so much was the fact that the flat seemed like it could use a little bit of maintenance. There was a lot of marks on the walls and generally signs of use. And the flat could have been cleaned a little more thoroughly beforehand.