On arriving at the apartment, which was very easy to find from the nearby airport bus stop, Maria was there to meet us as agreed. The apartment was exactly as depicted and described on the website - it was huge and centrally located, ideal for a family or a group of six people or so.
The kitchen was well equipped (great coffee machine), while the WiFi and TV both worked well.
The surrounding area contained a good number of nice restaurants and bars, and it was only a few minutes walk to the Brandenburg Gate and the Reichstag, with the S/U-Bahn a similar distance in the other direction.
All in all, I'd definitely recommend this flat and host to anybody looking for a comfortable, relaxed stay in the centre of Berlin.