Gravity lunatics swear by the basic Hayes brake and it's obvious why. The long lever and big 203mm rotor means stonking stopping power (a 229mm upgrade is due soon), although the blunt, abrupt feel means control is learnt, not guaranteed.
The brake's legendary reputation in the mountains was backed up by excellent performance on the dyno, with the rotor only warping temporarily at temperatures you'll rarely see on the hill. The original Hayes slotted post mount makes fitting very easy, and either lever can be run on the left or right. Bedding in is fast, pad life is long and overall reliability is excellent. Various upgrade options are available and it's not that heavy either.