We enjoyed staying at John's place which is spacious, tidy, and bright.
All the rooms are as they appear in the pictures, and the two terraces are quite nice on sunny days.
The communication with Frank who administers John's place went well. Frank answered all our messages very quickly and thoroughly. We found the pick-up system for the keys very clever (we picked up the keys at a local bakery).
We stayed 5 people in John's place, and it would have been easy to stay a couple of more people since it's so spacious.
You can walk to the address from the S-Bahn in 5 minutes, and there are several supermarkets at the station. You can walk to the center of Friedrichshain in about 15 minutes.