Great place to stay. Location is the best. Communication with Turkhün was really good even though we never met. He called a couple times for updates, even before we departed for Turkey and gave great tips for things to visit and places to eat in Istanbul through whatsapp. Check in was really easy with his instructions. The view from the terrace is incredible, great place to have a drink, listen to some music, sit back, relax and enjoy the view (and the cats on the surrounding rooftops ;-)).
Only thing worth mentioning is the appartment is narrow. This was not a problem for me as I visited Istanbul before and know this is simply how it is, especially in Galata. But if you are a big guy, this could potentially be a problem. We just barely managed to squeeze ourselves into the shower for example.
All in all a great place to stay, will come back when visiting Istanbul again!