I had a lovely stay with Hedda-Maria. The room was clean and and comfortable, and the house is situated in a very quiet and beautiful place. It is a bus-ride from the S-bahn so definitely it is best for exploring the area, rather than a base for seeing central Berlin. It is very handy for Wannsee and Potsdam, and good for hiking into the forest.
One thing to note - the apartment is listed as 'entire rental unit' but it is actually a room in Hedda-Maria's house, so this one detail in the listing is inaccurate.