I really enjoyed staying here - I was here for six nights. Aside from the apartment's proximity to transit (a 6-minute walk to Schönhauser Allee U-Bahn station), I can say that Bernd and Katja are very very friendly and helpful hosts, the apartment is quiet and exceptionally clean, and that I'm very happy I chose this apartment to stay in when visiting Prenzlauer Berg.
Bernd and Katja met me at the door to the apartment to walk me up and show me the place, and let behind a bottle of wine that was a nice touch. The apartment is small, but has everything you could need for a fairly extended stay. One of the things I appreciated most is the ability to control the temps. Since the apartment is a few floors up, it gets hot. I was able to open the kitchen window and balcony doors and freshen the place up in just minutes.
The street is quiet, and the apartment block is very quiet as a result. The apartment faces the courtyard of the building and not the street, so I didn't hear any of the typical Berlin sounds, such as recycling being picked up, or car horns (the street is narrow, with cars parked on both sides, but it's a two-way street so I saw more than one shouting match as cars tried to squeeze past). On that note, I shouldn't like to try to park on that street, day or night.
Lovely place. Would stay again!