We spent 5 nights in Daniel's apartment and had a great time in Istanbul. As already mentioned in pretty much all other comments, the view from up there is amazing! Daniel was helpful during our visit, although we had no chance to meet in person. He was always available via chat. For us, the apartment could use a few lights more as it can be a bit dark, but that also gives more of a romantic touch to it. The flat is located very near to Tophane tram station which makes it very useful to explore the city. To Istiklal and/or Shishane station you will have to walk up the hill.
Overall we can very much recommend this flat to anyone :)