We stayed a week in Ulla's apartment, and everything was as we had hoped! Beautifully decorated, extremely well-kept apartment that could easily accomodate a group of 10 people. The first thing we said when seeing it was: "let's buy this place right now!" The fact that it is on street level was simply a plus, since we could wheel our Buggy straight in.
Ulla and Andreas was really friendly, and easy and fast to communicate with both up to and during our stay. A great place to visit Berlin with family. We'll definitely be back.