For 2012 XTR gets a new rear derailer, dubbed the Shadow Plus (RD-M985). It has a heavier spring and a gold colored two positions ratcheting switch (On or Off), which they call the stabilizer. The system consists of spring with a one way friction pivot or ratchet gear, which is enclosed by a band clamp. The Off position moves the clamp upward away from the pivot, allowing free cage movement, and when the clamp is down, it tightens the pivot up, constricting movement or increasing friction in the forward direction. When engaged, this increased pivot friction, dampens the cage,  quiets down chain noise, decreases chain slap, and helps alleviate any chain drop offs. When the switch is Off, the derailer acts like a standard Shadow, and this mode makes for easier wheel removal and drivetrain fine tuning. I played with this at the show, and it makes a dramatic difference, and will make flying through rough terrain and rock gardens much more enjoyable.