We stayed in Marco and Deniz's apartment on a family trip to Istanbul. Marco met us in person to let us in the apartment and gave us a tour. The apartment is spacious and easily sleeps 8 people. There are also two ACs, that help in the summer months (when we visited). Marco was helpful during our stay, there was a issue we called him for, and he was responsive and solved the problem. The apartment has a very nice terrace on the 7th floor, overlooking the city with a beautiful view. Without going up the rooftop terrace, you'd enjoy a beautiful view of the sea from the windows of the apartment too.
One thing to take into account is that the apartment is on the 5th floor in a building without an elevator; something to consider if you're traveling with the elderly or with a lot of luggage.
Overall, the apartment was very nice, spacious, clean, and the host was great! I would recommend Marco and Deniz's apartment to anyone!