I had a pleasant stay at Eric's place, which is very centrally located but still calm and quiet. Both the room and the bathroom were superbly clean. I didn't have a chance to meet Eric in person but he was always responsive to my messages/questions and gave great tips on things to do/places to go.
While guests do not have access to the kitchen the guest room features a coffee machine, a kettle (and tea selection for tea-drinkers), and a small fridge (which gets a bit noisy at night, but can always be unplugged). The room is fairly sized; in addition to the bed, there is a wardrobe and a small sofa. One thing to keep in mind about the room is that it has one small window facing the courtyard and not too much daylight comes in (which would not create any problems if you are not planning to spend too much time in the room during the day). All in all, I would happily suggest Eric's place to anyone visiting Berlin.