A great place to stay, especially if you're going to have a more laid-back trip to Berlin. Maybe not the most ideal for someone interested in seeing Berlin's nightlife.
The apartment was exactly as shown in the pictures, very clean and plainly, but comfortably decorated. It offered all the basics you might need during you're stay, including sheets, towels, dishes and a map that you can borrow.
Communicating with Heidi was very easy, and she was flexible with check-in and check-out times, we even got to leave our luggage at the apartment after checking out. We had a small issue with the lighting system, but both Heidi and her husband were very kind and attentive, and got it fixed as soon as they were able.
All in all a great stay, and good value for your money.