A&O is an older hostel, and it shows. Compared to other hostels in Mitte and area (Circus, Generator, 180) it's a dinosaur; however, if all you need is a roof over your head A&O will do the trick. That said: cleaning staff were in the habit of barging into my room (hotel side, not hostel) each morning at 9:30 or 9:45. I also ran into trouble after I asked to store my bag for the afternoon after I checked out and their very limited pay-to-use locker system simply didn't work. I was not the only guest experiencing trouble and the staff were either unwilling or unable to help. Front desk service also tended to be slow as there was only ever one person at the counter as far as I could tell. After seeing some of the other more modern hostels in Berlin I will not be staying at A&O again if I return.