I stayed in this apartment for 41 nights in August/September 2018.
Bottom line: warmly recommended for a great location, well-designed space, and very friendly and responsive host.
Other pluses: great kitchen; amazing and faultless wifi; easy access from front door of building down a couple of steps.
Special note: Mark was prompt, friendly, helpful, and easy-going in all our communication.
Minuses: No big minuses here. The apartment isn't very light. The shower cubicle could do with an anti-mold treatment. You may need to buy a few extra pieces of equipment in the kitchen. But these are very minor issues. Generally - a great place ready for you to come in and use as your home in Istanbul.