It was offered as an apartment but it was actually a room in a hostel (no kitchen, no privacy if i.e. you invite someone to your room since there was a person controlling at the entrance all the time). That was very disapointing when I find it out at my arrival. The location for me was not the best. Taksim square is very lively, but it is far away from main attractions located in Golden Horn. Due to these two facts I find the price very high for what it was offered.
Kerem was nice and willing to help. There was another guy working during evenings that was not very helpful and always trying to refer you to ask Kerem at the next day.
I would not recommend to contract the private transportation from Airport to the hostel. Its extremely expensive for Turkey (25 euros from Ataturk... ). Other options, Havabus (stops closeby and its only equivalent to 2-3 euros). Bus stop is difficult to find, I recommend to plan the arrival carefully.