Overall, a good choice.
Positives: The location of the apartment is great. You have access to many means of transport such as Bus and Marmara by foot. You can also take a bus and 10 minutes later you're at Kadikoy. From Kadikoy you can take bus to IST airport. Also the apartment has air-conditioner which is nice.
The only important downside are the beds. Too soft that gave us back pain.
Also Ahmet is very friendly. He let us checkout later because of late flight time.