I stayed one week in this apartment with my parents. It is located in Kadiköy a region in Istanbul where was recommended by my friends from Turkey.
The location was nice considering that it's only 15-20 mins far from the Kadiköy port by public transportation. You have a bus station right in front of the building and there is a Metro bus station nearby that takes you to Marmaray train line that connects you to most important places in Istanbul very fast.
Also you can find many supermarkets and restaurants just by 5-15 min walk. There is a local traditional bazar near the building which is held at certain days during the week and you can find very cheap goods.
The apartment itself is on 21 st floor which gives you a fantastic view especially at night time and we really enjoyed watching it.
It was clean and tidy and it had most of the things I needed. The internet was high speed, the air-conditioning was quite efficient and you have necessary utilities in the kitchen.
I rented there for 4 people because my brother was going to visit us for 3 nights but the dining table was obviously not for 4 people and we couldn't enjoy eating on the same table. Also the sofa beds were not that comfortable for sleeping but the queen bed in the bedroom was very comfortable and nice.
Mr. Berkin himself was always available for questions and requests and is a kind person who let me check-in a little earlier because I had to leave my luggages and pick up my parents from another airport.
I have already recommended this place to my friends and I recommend it to the couples who want to visit Istanbul and enjoy a nice place to stay.