I have a pair.
If you already have rotors and disc mounts which fit, the brakes might just be worth buying at that price (the brake's sucessor, the Stroker Trail is £60 / end with rotors and mounts). There are a few other choices at CRC around the same price: Deore, Tectro. Unlike Shimano, parts are available for Hayes.
Power and modulation are good enough. With a 160mm rotor up front, braking on descents is "fun" (63 Kg rider), will I stop in time? Definately adds to the excitement.
Be careful when removing pads, the post in the piston in susceptible to bending or breaking away from the piston; it's not that delicate but should be treated with care.
Grease the compression nut before fitting. I had one of these seize, an attempt at removing it caused the master cyclinder to shear (cast not CNC).
Bleeding can be a faf. If reverse bleeding fails, the diaphram may be removed (requires removal of master cyclinder assembly from handlebar) and the brake bled from the master cylinder; this may be more difficult with fixed hose guides.