We had a great experience with Volkan. He wasn't around, but was responsive to our questions. Also, the people downstairs in the restaurant are super nice, especially the handsome young waiter, who seems grumpy but isn't, and they helped us check in, call a taxi etc. The restaurant, ominously called "Meat House" is actually better than average - we recommend the chicken chops and the Iskander Kebab. We ate there twice in a six day stay and we were happy both times in a city known for its cuisine.
The apartment is as advertised. Overall the place is a bit small, but perfect for a family or a group of 3 or so friends. It was clean and well maintained and the location is unbeatable. There are markets around, but they're touristy and basic - go to the Spice Bazaar and get cheese, bread and pastirma and you're set for breakfast.
The only downsides, which again were small, were that the street noise in the front room - the one with the 2 person bed - was a bit loud - we're early to bed folks with a young child, which means around 9pm. The noise wasn't obnoxiously loud, and was usully done by 10pm, so only be careful if you are a super light sleeper who goes to bed really early.
You are basically a stone's throw away from Aya Sophia, the Blue Mosque and Topkapi Palace.
Again, Volkan was a good host and we would stay here again.