I had an excellent experience at Fatih's apartment in Osmanbey. The location is superb, you can walk down to Taksim and it is on Metro Line 2 (green).

The room was sufficient, the kitchen was good - I was able to cook. The shower was a power shower and there was a washing machine, iron and ironing board.

Fatih was always available to answer emails and very helpful.
Thoroughly recommended!