We stayed in the apartment for 13 days and we really liked it a lot. You have there everything you need. The living room is really big with three couches and really comfortable. The kitchen is quite close and well equipped with dishwasher, gas cooking, fridge, electric kettle and coffee filter machine, etc. A really good thing is a special water supply for drinking water.
The bed rooms are at the other end of the flat and the mattresses are quite good. We did not have any back pain after sleeping, although we are quite sensible for that. The apartment has also a separate toilet in addition to the fully equipped bath room which is quite nice, when more people are in the flat.
The apartment is at the forth floor which was a surprise. However, the landlord was really friendly and helped a lot for transporting our luggage up- and downstairs. In general, he was really helpful and we could contact him all time in case of questions. He also provided the Istanbul-card for public transport and helped with the small problems we have had with one of them.
The apartment is really close to Taksim square - not more than 5 minutes to walk. There, is a Metro station which gives access to all directions of public transport.
So, we really can recommend this apartment for a longer stay.