I just went through extensively testing every 29er I could get my hands on.
XC Race: Trek Superfly 100, Specialized Epic, Niner Jet
XC: Kona Hei Hei, Khs Bajada
XC/ Trail: Trek Rumblefish, Specialized Camber
Trail/ All Mountain: Specialized Stumpjumper
And as of now I will be getting a Trek Rumblefish pro.
I ride what I call aggressive cross country, single track some jumps I come from bmx and do not sit down much. The Trek Rumblefish and Specialized Camber were my top choices. They both road very similarly, and have similar geometry the chainstay is 2mm diff, and bottom bracket height is 3mm diff, and there head angles at 69.8 for the RF and 70 for the camber. The ride is slack enough to not be twitchy but still steep enough to be responsive and agile. The Specialized Camber has a longer reach by about .5 inch which is a plus for me, allowing for a size smaller giving more clearance. The suspension is what tilts it to the Rumblefish, the extra travel is appreciated and access to better component levels at a reasonable price on a aluminum frame seals the deal. The pro comes with full XT and better shocks than the elite which has a SLX/XT mix. If I get a chance I would like to try the Salsa Horsethief and Tomac Diplomat.
The Specialized Stumpjumper has slacker angles with a head angle at 69 and also has more travel. The Scott Genius and lenzsport Mammoth looks similar, but I have not tried them. To get a higher level component package with the Stumpjumper requires going carbon.
The XC Race bikes had head angles around 71 which seemed a bit quick for my liking. For the XC bikes, the Kona was less twitchy with a 70 degree head angle and has a new stiffer rear end for with a shorter chainstay for 2013, and the khs was not a race bike.
Looking over warranty information where the XC/ Trail and Trail/ All Mountain bikes are classification 4 the XC Race and XC bikes are rated as classification 3 which stipulate the bike rarely leaving the ground. :\ Class 5 is north shore/big air and class 4 is some jumps, so, when they rate a bike class 3 and talk about not jumping and staying on the ground I think that's what they mean. I could not find Niner's listing or warranty information