We had a great stay at Cube Suites. Erol, Kuzey, and Yusuf were extremely prompt in their replies to our many questions. We flew into the new Istanbul airport and they were able to arrange transportation to/from, though since it is farther away we spent a little more on transportation than we were expecting (but that has nothing to do with our AirBnB stay!).
The rooms were exactly as described, though the wifi was a little weak in our second-floor room. We appreciated that there was someone available in the lobby at all times, to greet you coming in and offer you Çay, coffee, and cookies. All the time. And more than you could ever want! Location was an easy walk to the big sites, and close to transportation. They also have lots and lots of recommendations for things to do--though there is something to be said for just relaxing with tea and a hookah nearby!