After having stayed in AirBnb's across the world for many years now, I can say this was nearly as good as an AirBnb experience can get.
Location: right by Galata bridge, train, ferry, quick funicular to Istiklal, and nice walk through restaurants, dessert and coffee shops to Galataport. Only caveat is a bit of street noise at night.
Apartment: spacious and comfortable, thoughtfully decorated with an artist's touch. Super clean. AC's in all rooms.
Host / Check in & out: Yusuf & his team helped us with luggage on both check in and out. Yusuf was available throughout the stay as needed, and helped arrange smooth airport transfer on the way out.