Deniz's place is located in one of the best areas in Istanbul. it's surrounded by sweet cafes and good vibes, and close to plenty of transportation (by boat, bus or taxi). We stayed there on a very cold week, and the excellent heating in the apartment was perfect. Deniz was very kind with us all along the way, and allowed us to check out late.
However, you should know that the walls are very thin and we could constantly hear strong voices from outside the apartment. There was also a problem with flushing the water in the toilet. We contacted Deniz and he came to fix it, but the flow was still quite weak.