We just got back from our one week stay at Kürşad's apartment, and we really liked it. The apartment was perfectly sized for the two of us, trendy and comfortable. The wifi was strong and consistent enough. It's in a really good location, on a trendy side street just off the famous İstiklal Avenue (with metro connection). In the opposite directions, you have easy access to the trams and one of the best hamams in the city. There are also lots of nice restaurants, bars and shops around. Kürşad was also there upon arrival, very accommodating, and very quick to respond whenever we had a question.
The only downside was that it could be a bit noisy on Friday and Saturday nights, but it wasn't anything out of the usual. That's just the price you pay for being in such a central location. The other nights of the week are okay. The location is also a bit hilly, so if you have serious mobility problems this probably isn't the place for you.
All in all, it was a really good stay and excellent value for the money. We will definitely be back.