We spent a week at Safa's place and we had a real good time.
The flat is very well located, near Taksim (5 mn walk), in the very nice area of Beyoglu where you will find everything you need : bars, restaurants, shops. You can do a lot of thing walking and metro is very near if you need it. You have 2 small supermarket downstairs if you need anything.
The flat is nice, comfortable, clean and similar to pictures.
Safa is a very good host, talkative and friendly and very reactive in communication.
I highly recommend this place and would be happy to stay here again when I'll be back to wonderful Istanbul!