If you're looking for an amazing host, Firat is the one. He was extremely helpful in all possible ways. He even left us to stay more than our checkout. We had to leave at 11:00 AM but we stayed till our flight (evening 19:00). As for the apartment, it's exactly like in the photos, also if you have to work the wifi is decent (I am a programmer and I had no problem while using it). As for the location, if you have to go every day in Taksim that might be a bit of a challenge because it's uphill, however, if you have to visit different places (like I did) the Tram station is really near (mostly 2min).
Suggestion:
My taxi-driver had a problem finding the address because he was a bit old and wasn't using the GPS, if you're on a similar position I'd suggest to tell them to go to "Tophane" tram station and then call Firat to take you (is 2min from building)