I've stayed there for 4 nights.
At first it is located a bit far from the city center, but the great side is that it's in front of the tube... there are stores, shopping mall and restaurants really close to the hostel. There's nothing to see there. You'll need to spend at least 30 minutes to see London attractions (Tower Bridge, Hyde Park, Big Ben, and so on).
I didn't like the bed... it's noisy and uncomfortable. Another problem is that you can hear EVERYTHING from the street... I don't know if there's a hospital close to the hostel, but I've heard ambulance' sirenes the whole nights. I just got used to it by the 3rd night.
The pub Belushi is really nice. The staff is nice and helpfull. Nothing to complain about them.
