Absolutely amazing apartment - sunny, clean, accurate, quite, fully equipped.
The location is good as well - there are a lot of restaurants, shops, market. You can reach all other parts of the city by bus or ferry as there is a port and a lot of bus stops.
And special thanks to Seçkin & Duygu as they are brilliant hosts - they gave useful recommendations and advices (even a map with useful information).
A great place to stop in Istanbul.