Our family stayed in Cesim's apartments for a week. Overall we had a pleasant stay but it wasn't without setbacks. The apartments are located on a small but busy street at the bottom of the hill, the trams and tourist attractions are on top of the hill, the 8 min walk up and down the hill was a bit challenging for a baby and especially an elder person in our family.
We were five people plus a baby and we got two apartments on the first floor. They were clean, Cesim was quite helpful and arranged a transfer for us and ordered a taxi to the airport, even initially put a crib for the baby. The apartments had nice furniture and were very well cleaned on a daily basis. The kitchen was adequately equipped.
Our main setback was the windows in the apartments—they provided almost no sound insulation and some of the windows couldn't be properly closed. Since the apartments face either the street or the restaurant downstairs open til 1 AM and that Istanbul is a loud city in general and there is ezan, call for prayer, taking place around 6 AM, the apartments might be better suited for people who aren't sensitive sleepers.
Also the power outlets weren't covered, as stated in the profile. We had a small child with us and had to ask Cesim to put tape over them. Another setback was that the bathroom in one of the apartments had water damage and black mold on the ceiling. The window in the bathroom couldn't be opened and there was no extractor fan so the bathroom was uncomfortable after showering.