We had a great time at Arda's place. It's very spacious, nicely decorated and cosy, makes you feel at home straight away and has that unique vintage vibe you won't find in modern apartments. I was actually trying to come back home earlier every day just to spend more time there :)
The room is big, pretty, with lots of sunlight, there's also a huge balcony overlooking a yard full of trees and birds - a perfect place to chill at the sunset or in the morning.
The location is great too - it's on the other side of Bosphorus, away from tourist crowds and next to lots of cool local cafes and shops but if you need to get to the city centre it's just a 15 min walk and a ferry ride across Bosphorus. The airport shuttle bus also stops nearby.
We didn't get to spend a lot of time with Arda since he was away for the whole of our stay but judging by his book collection he must be a very interesting person
The only drawbacks I can think of are no fan in the room (and it gets really hot in Istanbul in summer!) and if you have heavy luggage beware that the flat is on the 4th (in fact 5th) floor and there's no lift.