Aydin's appartment was a great place to stay for us during eurobasket championships. It is located close to the airport, appx. 20 minutes walk from the Sinan Erdem hall and 3 minutes from the Atakoy metro station.
The place itself is very nice, clean and cosy, with the lone disadvantage of being located in the 5th floor, without an escalator. Aydin helped with our baggage and provided clean sheets and towels.
Aydin speaks perfect English, is reliable and flexible. Most messages were answered within an hour, every single one within a day. He even helped us with some personal errands and gave information about tourist attractions, metro system (even gave us metro card with some money on it) and other useful info. We had some complications with our booking dates but he generally made it easy for us and caused no additional trouble.
I highly recommend it and don't expect much better for this price in Istanbul.