I satyed for two weeks in Stefan's place and it was a great experience. He is a very sympathetic and easy going person, also very helpfull and avaiable when it's necessary. The apartament is really nice and it's very well located - close to a metrostation, oranienstrasse (lots of bars n restaurants), hermannplats, to the canal and parks. Lots of extra points because there is an avaiable bike - perfect for a city like Berlin during suumer.