We found David's flat to be a great place to stay for a weekend in Berlin. The location is within walking distance of many bars and clubs, and is easily accessible from the airport.
The flat was clean when we arrived and the kitchen was well-equipped.
As other reviews have mentioned, it was a bit noisy at times (ground floor flat, ongoing construction) so I would recommend packing earplugs -- but it seemed pretty normal noise levels for a city in summertime.