We stayed at Örücü Palace's Harem apartment which is located at the ground level and has a private entrance from the street.
The apartment easily accommodates four adults. It has two bedrooms. You walk through the first one to access the second one. There is a small patio accessible from the second bedroom. The kitchen has a gas stove and all the essentials. The bathroom is large and nicely tiled.
The apartment building is in a good condition and well maintained even if the building is old like most of the building in the center of Istanbul.
The location of the apartment is very convenient. If you walk uphills for about 500 meters you get to Istanbul's main walking/shopping/eating street. If you walk downhills, you get to the main street and to the tram line.
The host, Mehmet, was very friendly and helpful. He gave us a good orientation of Istanbul during the "check-in", and had maps and even a public transportation card for us to use. We had absolutely no problems during our stay at the Harem apartment.
We can truly recommend Örücü Palace as long as you don't mind walking up and down hills (but you really can't avoid that in Istanbul anyway).