We stayed three nights at Louis's apartment and we loved it.
This place is located in a nice, quiet and clean area of Neukölln, a few minutes walk to Tempelhofer Feld which used to be an airport and now it is a huge park. Every touristy spot is easily reachable by bus or U-Bahn, you only need to walk about four minutes to the station.
Louis seemed like a really friendly and helpful guy, and we would definitely choose to stay at his place again, on our next Berlin visit!