I highly recommend Chris's place! my wife and I stayed at Chris's place for 3 nights, and everything about it was great: Chris is kind, helpful, accurate and easy-going. his place is located in a cool area in Kreuzberg, just a spitting distance from U7 and nice bars and places to eat. the room was clean, spacey, and we were free to come in and out at any time. don't miss the great shower!
one of the finest stays I've had :)