We spent 4 days at Kürşad's place in February and had a very pleasant stay. The flat is modern and spacious, and very well located in the center of Galata which is a very nice area full of bars, restaurants etc. Metro and tram to join historic places are not far: 10 minutes walk to join Karaköy and 3 minutes to Shishane.
Besides, Kürşad is a great host: he was very available for us during our stay. For instance, he booked taxis from airport to the flat for us and waited until midnight to welcome us the first day.
I can only truly recommend Kürşad's apartment, and I am sure to go back to his place if I will come back in Istanbul on another occasion.