I really enjoyed my stay in Kenan's place. It's newly remodeled and very tastefully done, and in a great location for seeing all of sights in Sultanahmet (old Istanbul). It's a very short to walk to the Blue Mosque and Hagia Sofia, and there are an infinite variety of restaurants to try in every direction, in every price range and type of food.
The hot water, air-conditioning and Internet worked very well, which was particularly appreciated after a long hot day of walking when you just wanted to come inside, take a shower and collapse for awhile. The windows are very well insulated and eliminate almost all of the outside noise, which was quite amazing.
My only caution would be that this is a second floor apartment with a curving (but not spiral) staircase. It can be a little tricky with luggage.
I also highly recommend letting Kenan arrange the travel for you to and from the airport. It was just slightly more than ordering my own taxi, but he takes care of the directions, can greet you on arrival and most important, organize your departure so that you depart to the airport with plenty of time for your flight. The two vehicles I rode in were Sprinters with very nice interiors, so it was really more like an airport limousine experience than a taxi.
Kenan himself was a great host. He responded quickly when I had questions about where to meet the driver at the airport and gave me several great recommendations for things right around the apartment. He definitely wanted me to have a great stay in Istanbul, and it showed in everything he did. I'll definitely stay with Kenan again on my next visit to Istanbul.