Jens was great. He was very quick to reply to our messages prior to our arrival. We arrived to a clean and spacious room, with a bottle of water and a little nighttime chocolate for each of us. The block/area is VERY quiet (windows open all night and you couldn't hear a thing). Very spacious bathroom with unlimited hot water supply, and good shower pressure. Even though he lives in the apartment, it is in a room at the other end, and after we checked in, we never saw or heard from him again, so it was sort of like we had the place to ourselves. There's even a clean, spacious kitchen with a little 2-chair table by the window for a quick bite. There was also an older iMac in the room for guests to use, and of course Wi-Fi. The only things that could use some tweaking were the fact that there isn't a mirror in the room (so women who want to do their make up or check out their outfit before heading out on the town have to use the small mirror in the bathroom above the sink). Also, the shower box is a little small (granted I'm 6'6" and I've definitely seen smaller shower boxes (Japan, etc.), but even my girlfriend at 5'2" thought it could be a little roomier). Also, and this is just a heads-up more than an issue, you have to share the bathroom with the host instead of having your own private bathroom (but as we said before, we never saw him after check in, so it's not really an issue unless you're a heavy bathroom user).
Overall, great host, great location (2 blocks from the S-Bahn and U-Bahn, and 2-3 stops from the center of everything). Would definitely stay here again.