We stayed for 3 nights, and had a great time. The apartment is pretty close to Istiklal and the nightlife, but about a 10 minute walk away in a quiet, residential area that really makes you feel like you're living in Istanbul -- especially waking up with the beautiful view.
Erhan was really helpful and nice. We arrived quite late and had an early flight leaving, but he managed to accommodate, and offered lots of tips for things to do. Would definitely recommend.