We had a great stay at Isak's flat. Didn't meet Isak, but Kadriye was on hand to help with things. We were prepared for it to be noisy from reading others' reviews, so the Ramazan drumming at 2.30am wasn't too much of a problem!
One thing I would say though is that the mattress on the bed is really quite worn out and sagging in the middle, so we didn't sleep very well.
Other than that, it's a beautiful place and a really good base (great location) for exploring Istanbul.