A couple week ago I was flung this 2010 X9 rear Derailleur. It has totally been revamped. The design looks sweet. The finish is top notch.
The biggest advantage of the new design is how the profile of the derailleur is reduced by about 10-15mm. Fitting between rocks and the like without damaging your equipment will now be a bit easier.
To achieve this the cable now routes behind the main body. It gives the derailleur a total new look and allows for the reduction of the profile. As far as shifting goes, pure SRAM. I could not tell the difference when I replace my XO.
It has been on the agenda for a little while now, but I finally replace my old road group set with SRAM Force. Yet to be ridden but first thoughts are WOW. For the fun of it I weighed every item as it came off the bike and compared it with it's replacement. Every Force item was lighter than the Ultergra item excepting a 20 gram gain in the bottom bracket and equal weight of the cassette. Total saving was about 300 grams. Doesn't sound like much, but at the end off the day these two group sets are competing for sales and I know 300 grams would make a big difference when is comes to laying down your hard earned cash.