Communication by email was smooth. We were greeted by Jennifer's sister who explained all that we needed to know about the apartment which was stocked with a fresh fruit platter, chocolates and some flowers, very nice!
The studio is just as described and in a great location close to the S and U train lines, with good shopping and dining within walking distance but with a more quiet residential feel within the city (a 15 minutes bike ride to the Zoo - with the apartment's bikes as a plus).
Three of us stayed for 4 nights and it worked perfectly for us. Good kitchen and nice and large clothes washer and dryer. We would definitely stay here again while visiting Berlin.