Pivot Mach 4 X0
For the serious enduro and marathon racers, it is getting very hard to look past the bomber SRAM X0 2x10 groupset, with it's lightweight carbon cranks, wide range 10 speed cassette and punchy trigger shifters. With the objective of minimising front shifting, the X0 drivetrain is slick, dependable and crisp - a perfect match to the Mach 4's responsive and snappy handling. 
The Pivot Mach 4 is by far the most popular Pivot model here in Australia. The Mach 4 is a 100mm XC purebred that has struck a chord with many XC and Enduro riders around the country. For the latest model, Pivot have taken their extremely efficient, extremely stiff and extremely desirable Mach 4 frame and turned up the dial even more. They have stripped 285 grams out of the frame while lowering the standover height across the board thanks to a curvy hydroformed top tube that eliminates some of the welding that was required on the older model. For 2012 the stout Tapered headtube remains, keeping the steering accurate and the front end of the bike solid, though Pivot Cycles have made the move to spec the complete bikes with a 120mm fork, instead of the 100mm travel fork used on 2011 models. Having seen many riders make the transition to the longer fork, it seems that riders are demanding a slightly more plush front end for stability in the rough stuff, at the slight expense of climbing. We would have to agree with Pivot, as the 120mm fork up front serves to improve the Mach 4's prowess off road with very little compromise. Of course if you're exclusively XC racing, you can still fit a 100mm fork for quicker handling, so the choice is yours.