Great place. The apartment was very clean, had every essential we needed while traveling and was a great home base. Great location a short walk from Potsdamer Platz station and, during our stay, the Christmas market. Martin was a fantastic host. He had offered to let us check in early and was extremely understanding when our flight was delayed 2 hours and made sure we knew how to get there from the airport. He was there waiting for us in the apartment when we arrived to show us around and how to use everything as well as giving us some recommendations on what to see and do during our stay. And he even offered to let us keep our bags there after checkout as our flight was a later one.
I would fully recommend this place to anyone traveling to Berlin!