The apartment is 5 minutes walk from the most of the tourist attractions, close to the shops. It was clean and nice. Mehmet organized a transport for us from and to the airport, and also very quickly resolved the problem with the WiFi we had.
The only issue is - one of the rooms - has pretty small window, so it's a bit dark there in the daylight. But I assume that you will spend all the days out of the apartment to see the beauty of the Istanbul. So it doesn't matter a lot.
Highly recommended.