We stayed in this hostel for four nights in September and would definitely recommend it.

The people at the front desk were extremely helpful and were able to sort out any problems or queries we had quickly and efficiently. They were also fluent in English.
Our rooms were very clean and decently-sized. The beds were comfortable and there were also shelves, wardrobe spaces and safes. The en suites were small but clean and well-equipped (though the showers could be a bit temperamental) and shampoo, shower gel and towels were all supplied.

Breakfast was provided, which was a definite plus, and had a fairly standard German array of cold meats, bread rolls, fruit and cereal, as well as tea, coffee and fruit juice. There was also a bar (which could unfortunately be rather smoky), a football table, internet access (for a fee) and bike rental.
In general, the hostel had a great atmosphere. There were lots of people around, mostly teenagers and students, who were always willing to have a chat in the corridors or shouted out of windows.

The location of the hostel was ideal. Prenzlauer Berg is a young, hip district, and, while it's quite far out from the touristy centre, the excellent public transport in Berlin makes this almost negligible, since most places are only a ten minute U-Bahn journey away. The U-Bahn station is a five minute walk away from the hostel, and the street probably has most things you could want nearby, including a chemists, a Subway, and a good-sized shopping centre. Apart from that, the hostel is sandwiched between two excellent (and very cheap) Italian restaurants, so dinner isn't too hard to find.

In conclusion then, we really enjoyed our stay at this hostel. It's in a fantastic location, the staff are friendly and helpful, the rooms are great for the price, and breakfast is a bonus. Thoroughly recommended!