Sebastian's apartment is a true gem in Berlin Prenzlberg. We felt very much at home, and enjoyed every minute.
The unit is clean, and quiet. The bed was surprisingly comfortable. (I must admit I initially had some doubts but it was really great!)
When you close the window and the door, the bedroom is completely dark (I mean pitch-black) which was excellent.

One thing to keep in mind: this is a 6th floor walk-up. We had a lot of heavy luggage, and it took some effort to get it up the 110 stairs.
(But of course, once you see the view from either one of the two balconies, it was totally worth it. :-)