The apartment was amazing, as described. Very clean (which was very important for us) and spacious enough to fit 6 people.
The location is very central even if the cab got lost a bit, but it is very close to Taksim, so everything can be done walking. The neighborhood is charming. Lots of steep streets, but it's a good sport ;)
Yesim was really helpful, providing us with all the info needed, reservations to 360 bar and taxis when necessary. Great host!
I would definitely rent it again for my next stay in Istanbul.