Great location and value for money. The apartment is pretty much new as well as the amenities. You are within walking distance to several attractions , bars and restaurants day and night with the plus that the location is relatively quiet.
The place is very well run, there was person on-site at all times to help you check in and get you decent and affordable taxi to the airport and other recommendations.
Istanbul is a very lively city so there is a bit of ambient noise in particular over the weekend but nothing too bad that would prevent you from sleeping in my opinion.
The bathroom is very small but good enough for a short stay. Definitely recommend this place and would consider staying again.