My biggest problem was the lack of locks on the room lockers. The reception sells mini-locks for 40 Baht, but they are of horrible quality.
the only problem I've had was the moldy smell in the rooms, though that's probably a seasonal issue
Everything was good except the facilities (partially broken, lightbulbs missing, etc) and the lack of safety lockers.
Brand new hostel in Hamburg with excellent staff and superb facilities. Don't mind that it's not in the center - the local train station has trains every 10 minutes in the day and every 1 hour in the night.