I've got an Enduro Expert Carbon 29er on the way. It's got Specialized's "Taco Blade" with a specially-designed SRAM front derailleur. Specialized and Shimano agree that that's the only derailleur that will work on that frame. But I've already got a XT Dyna-Sys group I'd like to move over onto the new frame. It seems like a SRAM front shifter and a double crank would work, but is there a solution that would allow me to use a triple?