'Shifting and braking are noticeably improved. The shift action is extremely light... The brakes feel extremely solid. Even when paired with the current-style calipers, they felt lighter and firmer than their predecessors...
'Matt Robertson, Shimano's MTB product manager, confirms that the entire XTR group will be updated, right down to the middle chain ring, which is getting an injection of exotica in hopes of extending its life span. Shimano starts with a titanium core, which holds the ring's basic shape.
'The titanium is then covered with a carbon-fiber-reinforced plastic, which is the surface the chain actually moves over (the carbon also forms the shift ramps). This material allows for detailed designs that are too hard to achieve with a forged or coined ring...' More