Hi Nate,
I switched from an upgraded Gravity to a Trek Mamba for the Nocatee AR and I'll never look back. This Trek is 1/2 the weight and built for AR racing. The issue is the price. I have about $1,500+ in the bike after upgrading the saddle, tires, grips and pedals and adding a computer and lights. My suggestion is to get on craigslist and shop for a good Trek, Specialized or Cannondale mountain bike. Do some homework on each home page before buying. You should look for a hard tail (no rear suspension). It lessens the over-all weight. Make sure it's sized right for you. Go to a local bike shop and get sized. Also another huge suggestion is look for a 29'er. 29" wheels vs. 26" wheels. Huge difference. Trek's home page does a terrific job explaining the geometry behind the increased diameter. Maneuverability is not an issue since introducing Trek's G2 technology designed by Gary Fisher. In any event, I hope this helps. Good luck and I'll see you at a Pangea event again sometime in 2012.