I spend one week in this apartment and based on my experience I can say that this apartment is perfect for two people in many way.
The apartment itself is not really big. Bed, living room and kitchen is all at the same room but distribution makes it really comfortable. Maybe I missed a place to rest and watch TV that is not the bed, but who spends many time watching TV when in Berlin anyway.
Bathroom is really small, if you are tall or big can't be a bit uncomfortable, but it was OK for us.
Location is really good, well communicated, you have both U and S that take you anywhere you want.
The neighborhood is nice, you have anything you may need close by. Supermarkets, bakeries, drugstores, restaurants, even shops and sport centers.
We had a very pleasant stay and I would reconnect this apartment to anyone going to Berlin more