We had a great time at Nahide's place. The apartment is spacious (we were a couple, but it will be suitable for two couples as well), and has a truly amazing view towards the Bosphoros. We stayed during the winter, and the apartment is up to it - the isolation is good, and the heating works well; aside from the creaks of the windows when there's wind, you won't be able to tell it's winter outside. The apartment is located at the 3rd floor with steep stairs. It's in a picturesque area with winding, narrow streets. As for location, the apartment is about 10 min walk from the T1 tram, a short walking distance from the old-city attractions (Topkapi palace, the blue mosque etc.), and there are mini-markets and a supermarket nearby. Nahide was helpful and quick to answer, and was gracious enough to allow us both early check-in (as there was no guest right before us), and to leave our luggage in the apartment for a couple of hours after checkout.
Overall, highly recommended.