Freidrichshain is great so definately nice to find a good apartment there. Typical value for money stay, don't expect fancy vintage furniture etc. The apartment was clean, everything worked, we had fast wifi, comfortable beds en nice showers. We did not spend too much time inside the apartment because Berlin was just too much fun. Wolfgang was very kind and helpful, he showed up as soon as we gave him the call that we have arrived. He showed us around and gave us the necessary information.
So, summarizing: great value for money stay in a nice neighborhood!