Isik received us perfectly, explained all the place's rules and gave us good advises, and even had a great (and useful) detail of lending us a Card for transportation.
The studio is huge and really clean. At our time there, there was a noisy construction next to it, but the sound proof windows really made the trick.
The location is good (close to the Taksim square to take the metro to all the touristic places).
Big Con: 4 floors by stairs! Consider this if you have troubles with it (and remember you will probably have luggage)