Our group was 5 adults, incl. one couple. Nice location (2 stations away from Alexanderplatz), enough space, everything as described.
Our stay was during unusual for Berlin hot days (30 degrees and above) and since there is no AC it was really hot in the bedrooms. I do not expect any problems during normal weather.
Wi-fi works great. Friendly hosts, late check-in option really helped us a lot.
I recommend the place for a stay at a decent place and a reasonable price.