We really enjoyed our stay in this apartment. It's exactly as it looks in the photos. Very clean. Great location, close to the u-bahn and lots of cafes, restaurants, bars etc nearby. It also has a nice balcony.
We never got to meet Boris but he was very quick to respond to any questions/requests we had ahead of our arrival. He had arranged for someone to let us in to the apartment and collect the keys on departure.
I would recommend this apartment and Boris as a host to other people visiting Berlin.