I will definitely be staying at Mustafa's hotel when I return to Istanbul. It is very close to taksim square (6 - 7 min walk). However, it's not the traditional airbnb experience since this property is more like a hotel, but the room and its amenities (which included a full service kitchenette, bathroom, slippers, tv, wifi, AC) was top notch, modern, clean, contemporary, new and spacious. It was the only accommodation my friend and I stayed at throughout our trip in Turkey that actually had an AC unit! It's too bad that we only spent one night there.
Mustafa as a host was very accommodating! I think he even upgraded us (not sure), but he also allowed us to do laundry and even hung up our laundry for it to dry. The next morning when we checked out, he even gave us turkish delight as a departing gift.