Firat's place is excellent and well-appointed, with all the amenities a traveler to Istanbul could need. The washing machine & ironing board are great touches! His flat is situated in Beyoglu, a local area with tons of eateries and cafés - all devoid of tourists! At the same time it's not far from the main attractions, you're always a bus ride or two away from them.
I recommend everybody to stay with Firat, he's a nice and helpful guy, and his flat is amazing!