In reply to Darren09:
I have owned at various point in my life: Shimano Deore (various years), XT (also various years), Hope M4 (or equivalent 4-pots, also various years), Hope C2, and briefly some Hayes 9. I have also ridden a fair bit on bikes with Avid Juicys.
My take is this: for simplicity and power, you can't go wrong with Shimano. They are breeze to install, even if you need to shorten the cable, and easy to change pads and bleed when required. Power-wise: deores are fine for anything in Britain; but on longer Alpine descents they are out of their depth, and XTs or Saints are a better choice.
My one criticism of Shimano brakes is that, when they go wrong, you can't take them apart properly - i.e. when the seals go (which they eventually will) you can't replace them individually, you have a spend the money on buying a whole replacement caliper/lever. Compare and contrast that with a 10 year old Hope M4 which has now been through several rebuilds and is still working better than ever. The only problem is that Hopes are trickier to setup for good performance - but once you've sweat the blood/tears to get them working perfectly, they are extremely dependable.
So, in summary: Shimano for cheap and easy power; Hope for longer lasting quality (at the cost of extra faff with setup).