Price/quality of this apartment is exceptional. The location is unbeatable for comfortable life in Istanbul, and the neighborhood (Moda) has the best sunsets. It is a very safe area too (despite being always busy with people).
Apartment is full of light even though it faces North. There's never direct sunlight in your windows which is a lifesaver during the hot summer days.
Btw, despite the fact that the apartment is on the top floor, there is always a good water pressure, and hot water never ends thanks to the gas boiler.
Kaya is a very good host. He met me from the shuttlebus stop and helped me with my heavy luggage and even gave me a short tour of the neighborhood. He is always in touch if you have any questions.
Oh, and one more thing: Kaya will warn you about this during the booking, but I would emphasize this too - this flat is located on the top (5th) floor of the building, so it is more than 60 steps up the spiral staircase. If you have any issues with mobility, it would not be a good choice for you.
Otherwise, it is a very nice place to stay and I could definitely recommend it :)