Stayed here for a month, and it was perfect. First off, the location is in the middle of Moda Kadikoy, with literally 20 different cafes, bars, restaurants within a 5 min walk. At the same time, you get virtually no noise from the outside at night when everybody's partying.
Ali and Deniz were away for most of my stay, but were always in communication with me if I needed something. Ali gave me tons of tasty restaurant recommendations and places to see while in Istanbul. I also got to take care of Ghost the cat, who is the most lovable, adorable cat ever. I am officially a cat-lover now.
The room and common areas are very spacious and clean. I appreciate how organized and tidy they are as roommates.
If anything, the internet could be faster and a bit more stable. However, I was able to work from home just fine 99% of the time.
All in all, if you're planning to stay here for a few days or months at a time, do it.