We decided to stay at Martin's apartment during a short trip to Berlin - and we couldn't have picked a better place.
He was on time and welcomed us in a lovely way as we got to the flat: he explained everything about the apartment and how to move in the neighborhood and reach the main tourist spots. The flat was in a very good location - 10m walk from Potsdamer Platz, and a few minutes from the subway. It was also very quiet and comfortable - perfect for a short stay and it did correspond to the description on the website.
Highly recommended!