A large room with high ceilings, lovely parquet flooring and huge windows. The room is as it appears in the photos, although there's now a really nice/interesting table in the room that wasn't in the photos. Plenty of plug points, wifi, a selection of books in English and German on the bookshelf, shared bathroom, kitchen and living room.
During my stay, I was out most of the time, so didn't really get to socialise with Timo and the others who live in the apartment, but all were friendly and polite when I did meet them. On my last day, Timo let me stay in the room for a few extra hours after check-out because my flight wasn't until much later in the day, which saved me from having to carry my bags around for hours on a very warm day. I'm not saying that will always be the case, but it was for me on my last day.
Location is great for public transport. The nearest Ubahn (underground) station is a couple of minutes walk from the apartment. Berlin has great public transport generally, but it's great to be able to access the network so easily.
I'm a smoker and this is a non-smoking place. I hope my going in and out of the apartment at strange hours to smoke outside wasn't too much of a disturbance for the others living in the apartment.
I'd recommend this Airbnb place. It's great value. The Ibis Hotel across the street was charging €61 per night while I was in Berlin.