We spent 7 days at the apartment; 2 grown-ups with 2 kids. We were welcomed by the host and additionally all necessary information is provided in a booklet in the apartment, as well as some interesting Berlin-related reading.
The place is furnished in style and with attention to detail, the kitchen has all necessary utensils.
What is additionally convenient when staying with kids, is the playground in the courtyard and a 'baby-set' provided by the hosts. There is also a huge park nearby with playgrounds and a mini-zoo and a couple of good restaurants.
The only downside we can think of is that you decide to sleep on the sofa in the living room (as we did; the kids were in the proper bedroom), it is quite loud. If you are just two people, however, and sleep in the room which faces the courtyard rather than the street, you don't have that problem.