I rented this place for my family visiting Istanbul for my wedding.
Location is great, the view from the roof terrace is stunning, apartment is pretty and well equipped, communication with the owner is rapid.
However, there was only one big sized bed, other three sleeping spots are small beds so that my parents had to sleep apart from each other, plus the biggest salon (the main place for family gatherings) and one of the bedrooms has no air conditioner, which made those rooms almost impossible to stay in during the mid-summer time.
But the biggest issue was the wi-fi which didn't work within few days in a raw and it messed up our plans (because my sister works online so she couldn't work, and also I stayed separately in a hotel with my fiance so I couldn't contact my family (that doesn't speak English or Turkish) anyhow, plus I had to manage fixing internet issues while having million others with wedding organizations - that added me a lot of unnecessary stress).
The owner replied constantly, but the issue was solved only after a few days (right in my wedding day and only thankfully to mobile roaming internet that I luckily had). I would advise to change the "ancient" router in this apartment, because it is not a cheap place at all to pay for and have this kind of important issues (wifi nowadays is a must, people who afford this kind of places to stay during travel to big cities are generally kind of "business ones" that can't allow themselves to stay offline for a while).