Engin's apartment was great! We had a great time staying there. He was commutative, helpful and responsive and got back to us about our concerns promptly even in unusual hours. Couldn't ask for a better host.
a comment about the location since not everyone is as familiar with Istanbul (I wasn't): (not a criticism, just trying to be helpful to other guests) The apartment is close to Taksim, Istiklal and many local shops and restaurants as stated, all it takes is a quick walk to access whatever you want, and some small food places around have amazing food! However, it's not a very flat neighborhood. If you have asthma, serious knee problems, or any other chronic illness that makes walking uphill too hard for you, maybe research more before choosing this place. I have a feeling that Engin will answer all your questions patiently.