There isn't much to say about this wonderful place that hasn't been said, but it would be a crime to stay there and not say hire great it is.
The apartment itself is exactly as the photos shows. It has a really nice feel, modern and simple. Nice comfortable bed and a nice sitting area at the back.
Işıe is an exceptional host. She makes you feel at home, quickly catches on to your particular interests and style and adapts her content to that. She is without doubt the best host/ess I've met in my travels.
I loved Balat. I think it's fair to point out that some people wouldn't. It's a very simple and even area. I felt totally safe but some people might feel uncomfortable or self conscious. But for a taste of authentic and almost un- touristified Istanbul it makes for a unique experience. It won't stay that way for ever so it's worth seeing while it lasts.
In a word: go!