They're not superlight - but not very porky either. Mine weighed in at 512 grams (XTR BR-M965-R rear IS caliper + ST-M965 right side lever, incl. SM-RT96 rotor w/lockring, metal pads, 1230 mm hose, bolts and oil) and 516 grams (XTR BR-M966-F front PM caliper + ST-M965 right side lever, incl. SM-RT96 rotor w/lockring, metal pads, 710 mm hose, bolts and oil) respectively. Not too shabby I think.
Shifting with dual control is fast and precise, in short, excellent and in fact the very reason that I use them. Takes a little while to get used to and I would strongly recommend that you try before buying - and do it on the trail rather than a parking lot. Personally I find it very intuitive even though I don't use the rapid rise XTR rear derailleur but rather a RD-7800 DA instead.
Braking is very good compared to other systems I've tried. Modulation is fine even with the metal pads I use since the resin ones wear out way too fast for my taste. There has been problems with sticky pistons on some systems but it seems to be ironed out now. Mounting and bleeding is fast and uncomplicated.
If you don't fancy using the centerlock rotors and XTR hubs the calipers work fine with a wide array of rotors. I personally use Magura Marta rotors for my other wheelset.
The plastic parts scratch easily and replacements are hard to come by, at least here in Denmark.
