This cozy, beautiful little flat overlooks the Landwehrkanal and is located in one of the hippest and most exciting neighborhoods in Berlin. I love the market directly outside on Tuesdays, Fridays, and Saturdays––even if you don't want to buy anything, it makes for some very fun people watching and a feeling of excitement/being in a 'happening' place.
Matthias himself is a darling. We have had very clear and easy communication, and I am very grateful to him for helping me with some bureaucratic documents that were required for me to establish residency in Berlin for my academic fellowship. He is a truly unique and special individual. (I highly recommend his very amusing travelogues, "The World is My Oyster: Around the World in 30 Stories"... )
In sum: this is a fantastic place for a medium or longer length stay in Berlin. You are centrally located and close to 3 UBahn lines (U1, U3, & U8), are within walking distance of everything you need, and you are bound to have a lot of fun.