I was staying for a week there.
I've liked it a lot. It is a cosy, bright and large apartment. There is everything you may need during the stay. Utkan and Tulug are welcome and attentive and ready to help if you need anything. Wi-Fi is stable and fast.
One may doubt or consider to prefer Fatikh/Beyoglu areas. I'd say if you come to Istanbul for relatively long time, say one-two weeks, Kadikoy in my opinion would be the best place to stay. The area itself is very vibrant and alive.
The apartment is 10 minutes walk from Kadikoy ferry station, is a nice neighborhood.
All in all I definitely recommend.