In my eurotrip so far covering 8 cities this was the worst hostel.
The toilet is like a river with water all over
There is noise All the time (puberty kids running all over the place)
Our key card suddenly stopped working several times
The room is so hot because there is a lock on the window. In order to get off the lock every room member has to sign a paper. Wtf!? German mentality at its best?

This was my second stay and if your travelling with freinds and want to stay in a great area of the city this is a good option. It's really clean, of course it's basic, it's a hostel, however has a good bar, good staff, very close to a train station with great links so thoroughly recommend this hostel.

We spent just one night in the A&O in Friedrichshain in Berlin. The room and the attached bathroom were clean, beds were comfortable. Furniture and interior were basic but in a good condition. The room was quiet spacious. Reception staff was helpful. Although the hostel was fully booked there was only little noise at night. The location in Friedrichshain is nice if you want to spend some time in the lively and hip quarter of Berlin. Also famous Kreuzberg is not far away. You will find easy access to public transport that takes you everywhere (about 30 minutes to Alexanderplatz).

I stayed in room 102 for two nights (Friday-Sunday). The room was simple and the mattress was quite thin. The bathroom was nice but small (I could bearly fit my hands in the sink.) I only payed $120 for two nights, so I didn't expect much more. But the doors in the corridor was far from quiet. I wasn't disturbed by people, but every time the doors were opened, they closed with a bang. I guess the building wasn't built as a hotel.

Unless you're a light sleeper, I would recommend this hotel/hostel. It's a 5-6 minute walk from the S-bahn (Ostkreuz), and the trains go all the time. There are several bars and restaurants in the area.