I stayed here with my boyfriend from the 17th to the 20th of December 2016. Highly recommended for two people. Excellent, spacious apartment with very comfortable living/sleeping space, large rooms and fantastic location. Very close to local supermarkets and restaurants for immediate convenience, also very close to U-Bahn station for reaching everywhere else (and the public transport in Berlin is extremely efficient and organised). Apartment has washing machine, dishwasher, free wi-fi, gas hob, oven, toaster, kettle, plenty of crockery and cooking equipment, DVD player and television, radio, and plenty of storage space for clothing. Birgit is easy to communicate with and very fast at replying to any queries that we had, such as where to leave our keys when we left. Our plane arrived into Berlin at 10am and Birgit allowed us to check in as early as 12pm, 4 hours before the designated check-in time, which was much appreciated.
Small note that there is no shower curtain in the bathroom, so be prepared to wipe the floors and sides with a towel after you shower as it can make a lot of the bathroom quite wet! A minor point though, all in all a great value place from which to base your Berlin explorations.