We only stayed two nights, but the experience was great. Katharina responded immediately to our booking and gave us instructions for entering the apartment. This place is great because you don't need to exchange keys, so if you were to arrive at an odd hour it's really easy to use. The apartment is really clean, and the location is great because it's a very non-touristy area, yet easily accessible to the train station (for arrival with luggage), U and S-bahns, and just walking around. Excellent place!