Ok it is heavy duty. However the cranks are on par with profiles (a steelset of cranks) which offer more stiffness and strenght at an actual weight savings. However the cranks are sexier than profiles.
Many of my freeriding friends (the ones who the set is made for) hate the flippy shifters and have chosen to stick with rapid fire with the XT brakes. That and breaking the flippy shifter empties your wallet quickly.
The rear deraileur had some bad luck at the redbull because of breakage by 2 or the pros competing. However most people using them aren't having issues (40 ft hucks have a habit of breaking parts
)
All in all it is a good gruppo but you could put together something equally strong with a better freeride rear hub (it is still lacking the engagement points many riders like) for less then the gruppo price.