I stayed here for month working as a digital nomad and a tourist as well, so I have a lot of information to unpack for people who want to stay here. I highly recommend it for the average traveller, but I do not recommend it for certain types of travellers that I listed below.
This is honestly one of the best AirBnB I've ever stayed in the past decade. Reasons are:
Hospitality: Ceyhan is one of the best hosts I've ever had the pleasure of encountering with. I had wifi problems in the first week, he bought a wifi range extender and gave it to me within a day. Towards the end of my stay, there was a rattling noise that lasted throughout the night. The moment I informed him the next morning, the turned the place upside down immediately and was able to remedy it on the spot (something wrong with the upstairs unit). Always quick to reply, and always ready to help. Awesome guy.
Location: For the price, the location is beyond awesome. Convenience shops to buy groceries are nearby. Istiklal and Taksim is a less than 10 minutes walk uphill (very important to note this), and the Findikli Mimar Sinan Universitesi tram station on the main tramline is a 5 minute walk downhill. Also, the Findikli bus stop in front of the tram station has bus lines that connect to all major areas of the city that isn't served by the tram or metro (Besiktas, Ortakoy, Bebek). Also, walk a bit further from the station and you'll find the Kabatas Ferry Port, which I go to daily since there's a ferry to Kadikoy (the Asian side, which is my favorite place to eat). Just beware of scammers in the area though. I got scammed by a pair of people who posed as shoeshiners. Lost 90TL because of my ignorance. Read up on the usual Istanbul tourist scams people.
Room: The room is best for solo travellers like myself, because hey its a studio. Got a house guest for a bit of time and I can tell you that you can forget about having any privacy save one of you camp up in the toilet for the duration of the stay. Else, its awesome for a solo traveller. For a location so central, its so private and quiet. The room is tastefully furnished as well, easily one of the best decorated I've ever been in. Ceyhan is an architect and the main floor of the building is his office, I suppose that explains why its so well designed (He also designed the partner hotel down the road, Noble 22 Suites). Lastly, the amenities are very complete with electric stove, microwave, fridge, pots and pans, plates and cutleries. Bathroom is also very decent, although there should be some minor fixes that should be done (toilet is leaking a bit, towel hooks are loose and comes off the wall easily, shower head is problematic). Not a major problem for me though.
All that being said, I wouldn't recommend this place to travellers with mobility issues. In Istanbul you're either walking uphill or downhill, and there's little flat land save in the area of major tourist attractions. The building is on a steep cul-de-sac and also only have stairs, so if your walking abilities are impaired I seriously suggest you to find other places. Also, even with the wifi range extender, the wifi isn't good in my basement unit. I just circumvented the situation by using my data plan, which is relatively cheap for a foreigner. Working in the unit is convenient because of the privacy and there is a desk and chair, but the internet is spotty nonetheless. Just factor this in, but I'd say I had a great time working in the unit.
In conclusion, please stay at this unit. Awesome place and host. You won't regret it.