My family and I had an excellent stay at Katarina's!
First, you can't beat the location! The property is so close to many of the famous landmarks such as the Brandenburg Gate, Reichstag, Tiergarten, the Memorial to the Murdered Jews and a nice walk or quick bus/metro ride away to others like Checkpoint Charlie.
The apartment itself is clean and spacious. The beds were comfortable and we loved the huge windows in the dining/living room. Communication with Katarina was smooth and we were also able to check-in a few hours early. Overall, it was a wonderful stay and Katarina's place is highly recommended!