I stayed for 1 month.
The views are spectacular and truly one of a kind. You can basically see the whole of the Bosphorus. The generous windows can be opened. Imagine one of the best terrace cafes in Istanbul, except it's yours to stay in. When the call to prayers sound, it's like you can hear and feel the entire city.
The room is higher up than other buildings in the vicinity so there's nothing obstructing your view. As you go outside downstairs, you step right into the most lively part of Balat. It seems like half of the people on the street are taking selfies. It's a unique pleasure to stay in such a photogenic spot.
My favorite aspect of the views is that you can see so much variety. The ferries coming and going. The metro train gliding by the water. The birds swooping around the rooftops. The street vendors and musicians. The couples sitting in the park by the water.
Perhaps the most telling indication of how colorful and bustling the area is: in the 28 days I stayed, I saw 3 different movie/TV show shoots downstairs.
Selvi is a very nice person and will help you with anything.