We stayed week in apartment 9 and generally enjoyed it, especially the location in the heart of Galata and close to two tram lines. I would have given it a rating of 5 except for several deficiencies that made the place less enjoyable: 1) It is not well enough equipped to do any serious cooking. You can keep some things in the fridge and heat them up but there aren't enough pans and knives to do much else. 2) No dish rack or towel for drying dishes. 3) No shelf in the shower for soap or shampoo. 4) No bath mat. 5) The bottom sheet on the bed was not big enough to be able to be tucked in so it bunched up uncomfortably throughout the night. 6) The internet is unpredictable - sometimes OK sometimes very slow which might just be the way it is in Turkey. None of these things were serious enough to complain about but they would be easy to fix and make the place more useable and enjoyable.
However Omer responded promptly to all emails and Halit who seems to look after the building was very helpful. And the location is wonderful. I would definitely stay there again.
A tip for those who don't want to walk up the Galata hill from the Karakoy tram stop: There is a funicular that goes to the top of the hill from Karakoy. It's a bit hard to find but is in the bottom of the IETT office building diagonally across from the Karakoy tram stop.