Excellent location. Neukolln is the best place to stay in Berlin and still remains my favourite area. The flat is on a main road so if you're very sensitive to noise I recommend ear plugs but other than that amazing location, just 2 minutes from the U-Bahn.
The room is larger than shown in the pictures. Shower's great too.
I didn't see Mathias much as we were out a lot but he was great with both, my very late arrival and the last minute extra guest.
Will stay here again when I go back to Berlin next summer.