This is a great apartment in a fantastic location. We walked just about everywhere we needed to go. Anyplace that we didn't walk, we took the Metro, which was very convenient. We had breakfast on the roof terrace most mornings and had dinner there a couple nights as well. It was spectacular.
There is not much of a "sitting" space, if you want to relax and watch television or read, other sitting on a bed. But that was not a problem for us. We weren't in Istanbul to watch TV, and spent as much relaxation time as we wanted on the roof terrace.
I highly recommend this apartment. And Zenep and Ugur were very responsive with any inquiries we had.