Going to start with the negatives so you know it's a genuine review. It is in a great location for tourist visits, very central and easy to get to the main sites but with that, comes the crowds and the noise. Also, just so you know in case it happens, there was a day when the power (and hence the wifi) was out for a few hours. This was across Istanbul so it's not the hosts fault and nothing he can do about it (i.e. this is possible with all other Airbnb's.
Now onto the positive. I mentioned already but perfect location. Good value. Very communicative host. Big enough for 1 person if working from home or 2 people if just on vacation. Great restaurants all around. Can walk to the main sites. One of the best views of Istanbul from the rooftop terrace.