Friendly, helpful staff, and a nice, off the beaten path kind of hostel. Great if you're in London for a few days or a few weeks, but ask to avoid the 4th floor, where the elevator is incredibly noisy, and wifi completely inaccessible. The place is clean, and the onsite bar is open late with cheap drinks. (This is good, because the night life in Willesden Green is minimal).
Friendly and helpful staff, with great common room and tiny but effective kitchen facilities. Internet and wireless were pretty patchy, so tough to look up itinerary and area info online, but the hostel has lots of maps to borrow, and can answer most questions about the area.
On site laundry was a plus, as was the option to buy beer/wine/cider at the front desk. Pay as you go wireless should have a "for the day" option instead of a 4 hour cap.
Lovely hostel, with exceptionally friendly and helpful staff. Wifi was frustratingly inconsistent, but Castle Rock was otherwise a very nice experience.