The wifi there is called "a special retreat", it describes well the three days we had here with my boyfriend.
The place is clean and lovely, with a nice view from the balcony, the neighborhood is quiet and perfect if you want to spend some time around Kreuzberg for example (my advice is to rent bicycles to enjoy the city)
Martin was very kind and usefull to get our directions and there's a bus who goes straight to the airport (one minute walk to the bus stop)
Warning : there are more than one airport in Berlin!
nothing esle to say, did I mention that it was very clean?

Perfect place for two people, not in a center but as you will rent a bike, that's not problem