I stayed 4 nights with my wife, is an excellently located hostel with free good wifi, turkish breakfast, near restaurants, shops and, most important, the 2 principal attractions: Hagia Sofia and Blue Mosque
It’s a warm place, clean and with awesome staff, every one of them is happy to help
The only problem is that is noisy (or maybe the other guests were) and does not has an elevator
If I return to Turkey, I’d definitely stay there again