The apartment is absolutely stunning, and Berk is a truly wonderful host -- we highly recommend staying here! This was our first trip to Istanbul, though we've traveled a lot in Europe, and Berk was immensely helpful with our questions about getting around, where to shop and eat, and how things work. We walked the 5 minute to Cihangir many times during our 9-day stay for groceries, dinner, coffee, and just to stroll. And a few times, we continued to Taksim Square or to the other popular areas. We also walked downhill to Tophane to catch the tram to the Sultanahmet section, which was simple (though there's a bit of a hike back uphill on the return!).
Each time, it was easy to find our way -- the apartment is in a great location! We really lucked out!
And the apartment itself is amazing -- the photos and other reviews don't give a full picture of how delightful Berk's collection of art, furniture, and furnishings is. We felt like we were staying in an art museum!
In terms of staying in the apartment, it was very comfortable. We slept in the main bedroom the first night, but realized that there was a bit of street noise, so we moved to the second bedroom and slept there the rest of our stay. The kitchen is well-equipped, which we appreciated greatly, and we enjoyed the breeze that kept the apartment comfortable without using the air conditioning (during a hot period, 26-30 each day). The wifi was acceptable, but not great (as we've found in many places), so we avoided using video or having two of us using streaming / calls at the same time.
If/when we return to Istanbul, we will most definitely stay here again -- the apartment's convenience and decor, the great location, and Berk as a wonderful host was a fabulous combination!