Shimano XT M781 10-Speed Rear DerailleurThe new 10-speed XTR rear derailleur sees a re-engineered architecture that provides a smooth, linear feel at the shifter and is remarkably stable despite suspension movement, trail chatter or inevitable cable contamination.
I used one of these for 4 months. It is now in two pieces. It worked very well for about 2 months, and the Dyna-Sys clutch does work well. It does not work well on cassettes larger than 32 tooth, despite what shimano says. It quickly developed a lot of slop at every pivot, and the pulleys wore to their own unique shape. The cage is so thin, it will snap eventually if you ride hard. If you just xc ride, it is a solid unit. Don't put it on an all-mountain bike. Also, the cable guide rubs the cable on metal, so keep extra cables in your pack if you own this one. The older XT (9speed and earlier) are much better quality.