I've spent 4 months (not a mistake) at Mrs. Gudrun and can't have asked for a nicer room or nicer land-lady.
The room is spacious enough for one person, and Mrs. Gudrun is kind to share the internet connection (folks, remember, it is ILLEGAL to download torrents in Germany!)
Also, for me, I had a lot of help from Mrs. Gudrun dealing with Berlin's bureaucracy which she was more than willing to help.
The location, on the outskirts of Berlin is quite nice and quiet, yet you can find everything you'll need for your stay within 5 minutes walk: either grocery shop or the U- and S-Bahn stations.
I had an excellent time and warmly recommend staying with Mrs. Gudrun when you're looking for a place to bunk in Berlin.