We excitedly booked this place after seeing the nicely-done pictures. Upon arrival, we saw that it was quite different than depicted in the pics.
Cleanliness: Living room was disappointingly dirty (there were some marks on the carpet and armchairs). We found a small unidentified mark on one bath towel, maybe rust. Bathroom and bedroom were relatively clean.
Bedroom: The bed and pillows were uncomfortable- bed was sinking on one side. One pillow was sinking, too, so we wanted to use the spare pillows in the locker. We saw that these were smelly, probably last washed long time ago. Single-layer windows and walls were very thin - neighbors' talking & the azan from the very-nearby mosque at night were very noticeable.
Location: Best thing about this place, only 5 mins away from Istiklal and 10 mins from Taksim, walking distance from the airport-shuttle (Havaist). The building is very easy to reach and it's a nice thing to have an elevator inside (even though the flat is only in the 2nd floor). There are many local nice veggie shops, a few bakeries and and a kiosk around.
Communication: It worked well. Taner thankfully waited for our late arrival from the airport, and he took his time to recommend us a few places to eat a good dinner, and how to navigate around. But later, he ignored my message (didn't give a corresponding answer) about the bed & pillow issue mentioned above and we had to sleep the last night uncomfortably.
Security: After locking and bolting our door, I tried to open it while forgetting to unlock the bolt the next morning. Instead of the bolt preventing the opening, the wall support holding the bolt came down almost completely.
Otherwise no security cams or wardens (didn't expect anyway), since the building is located in a relatively suburb area.
To sum up: If I got a second chance, I would pay more and book a better place. We didn't get a good rest at night and it was not the best introduction to my girlfriend who came for the first time to Turkey.