I don't know Specific about the brakes, but a friend of mine put some on his freeride bike. He stated they felt better than the Hayes he had previously. His only complaint were the pads were crap, and changed them out for some all condition compound (not shimano pads) and said it made all the difference in the world! Other than that, I have no experience with them!
I'm waiting to see what the new XTR discs will be like!
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger