I cannot recommend Frank's place enough. It's located in a rather hip part of the city and is situated right around the corner from a U-Bahn stop that can take you to any part of town. Frank is a wonderful host. Although he was unable to greet me upon arrival, he made sure his friend was there to meet me and make sure I was settled in. I was on the go most of the time so I was only able to meet Frank once during my stay. He is absolutely charming and a gracious host.
If you are all a film buff (especially Fassbinder) you will truly appreciate the decor; it's truly a film museum!
A perfect way to spend a few nights in Berlin. A very bohemian place that suits the city.
Very highly recommended!