My girlfriend and I had a very nice experience staying at Shahrzad's very clean place. It's located some walk minutes away from Taksim square, from where everything is easily reached with metro. There's also a bus terminal in front of the house, where various lines start.
Shahrzad and Homa are very friendly hosts. They took also their time going with us around.
There are shops, supermarkets and a bakery nearby. There are also two cafés just at the corner - a traditional one and a modern one.
I woke up too late almost everyday and I didn't like the street noise which isn't supposedly formidable if you want to stay near the city center.
It's somehow confusing to find the appatment with the normal post address, but you can avoid it if you know the exact location i.g. On Google Maps before you arrive.
We recommend you definitely staying at Shahrzad's place.