I stayed in a 6-bed hostel room and overall it was decent value for the money. The positives: The bed was comfy with convenient shelves and two outlets, bathroom was clean, good shower. The building has a great equipped industrial kitchen and numerous eating/lounging areas, 24/7 bar with good and cheap drink options. Staff was very friendly and helpful, and there are lots of great places within walking distance - groceries, restaurants, clubs, and about 10 minute walk to the train station from whence you can get anywhere in Berlin easy. Now for the nagatives...
The "locker" was spacious but it couldn't actually be locked, even if you brought your own padlock... so don't leave anything valuable in there. Someone definitely rifled through mine looking for valuables, fortunately nothing was missing but it was obvious someone had thrown everything around.
The internet was TERRIBLE. Slow I can deal with, but they block EVERYTHING except basic web access, a nightmare for a remote worker like me. No VPN, SSH, not even Whatsapp or Zoom calls. Absolutely useless unless you're just browsing basic websites. Had I known it was going to be so bad I would have booked somewhere else, good internet is just a must for me.
Also, my room key stopped working every single day and I had to go down to the front desk and ask them to fix it. They would apologize and give me a new key, everything would be good until the next day when it would eventually stop working again. It would work at the entrance and hallway doors, just not at my actual room door, seemed like some sort of bug with their system (who knows).
Overall if you need a cheap bed for a few nights it's a great place. If you're staying longer (two weeks like me) and need good internet, look elsewhere!