We had a wonderful stay at Su's apartment. The place is beautifully furnished, clean, and has everything you could possibly need. The location is great too - all sights can be reached easily and there are plenty of nice cafés and restaurants in walking distance.
Communication with Su was great, she was always available and helpful. She was out of town when we arrived, but her friend Rami helped us with the check in and gave us great advice to get settled.
In a nutshell, I would book the place again when I come back to Istanbul :)