Stefans apartment was great. It was located roughly 15min walk from Alexanderplatz, however it had a number of train/tram/bus services nearby that can take you around if you don't want to walk.
The apartment building was very quiet, clean and well presented.
The apartment was quite large, with a big bathroom and washing machine. The kitchen was nice too.
The apartment overlooks a small park with a kindergarten right below. There's a great bakery at the front entrance of the building and heaps of restaurants and bars nearby.
Overall a great place to stay.