(Good things, many, at the bottom)
I removed one of the stars because the house hadn't been cleaned when we arrived. I removed only one star because the reaction was kind and fast. (Apparently, the service had been hired but they forgot; checking other reviews it looks like previous guests were happy so hopefully it was an isolated incident, you may want to check newer reviews and if they are OK, just ignore this point, we were unlucky). The cleaning service came later but in a rush and they forgot to clean the microwave and they left the used sheets piled in the closet. It didn't help that the previous guests were not the cleanest (when we got in the house, kitchen and bathrooms were really dirty).
The other star I remove is because of the risk due to the stairs. There is a picture where you can see one of them, it's more like a ladder (this ladder is taking you to the upper floor, where there is a bedroom and a bathroom). It's really steep and not convenient but it's not the worst. There is another bedroom + bathroom in the basement. To go down you have to open a trapdoor. If you close it every time, it's uncomfortable (the trapdoor is heavy, it's not easy to open and close it). If you leave the trapdoor open, it's dangerous. Also, there are two steps between the bedroom and the bathroom of the upper floor. We had a small incident at night. Take this fact into account if you are considering renting this house, especially if you are traveling with children or some person with limited mobility (the third bedroom with its own bathroom is on the ground floor, though, you can make it work).
On the other hand, the house was big enough, it has three bedrooms and three bathrooms (not very common!) and the kitchen is well equipped. They have done a good job with decoration, an old house that has been renovated to make the most of if (maybe renovation focused more on beauty than on practicality). There is a sofa and a table with 4 chairs (we had breakfast at home everyday). The place has little light (from the pictures it looks like there would be more but the house is surrounded by higher buildings) and little intimacy.
The area is nice, full of bars and restaurants. But the house is quiet, don't worry about noise. If you are planning to visit the most touristic area of Berlin it's far but very well communicated (5min from subway line U5, very convenient, it takes you to the city center and major touristic places). There are also a few tram lines close to it.
Hosts were nice, communication with them was easy and they always replied fast.