I stayed at Anja's flat for 1 month and it was an absolutely amazing experience. It is super bright with all the windows; the birds singing from the inner courtyard was always a great way to wake up. It was also really quite and I was able to sleep very well.
Also, Anja's flat is right in the middle of the Prenzlauer neighborhood and this is a fabulous area--It was very hard to leave and go see other neighborhoods. There are so many amazing cafes, restaurants, and parks. A major tram line is right out front (you cannot hear the tram when sleeping or even when in the family room) and it is super easy to get anywhere in Berlin, or beyond, from her flat.
Laslty, Anja is also very responsive in replying and communicating with her was always very easy.
I will definately be coming back!