Mountain Bikes are like religion, everyone thinks theirs is the best. There are many brands and each brand sells Econo Boxes and Corvettes with a ton of in-between models. My advice would be to find a Local Bike shop, A real bike shop not Wal-Mart or Sports Athority and take a few bikes out for a spin and then let your ass and wallet make your decision. Buying from a REAL SHOP will insure the bike is properly set up for you and was put together correctly. In addition you will have a place to buy upgrades get service when necessary as well as make some new friends to ride with. As for the Hummer Bike...If you do buy it, dont take it off road! It's kinda like a Jeep in that it looks capable but if you do it you'll break something, Could be the bike, you or both and when you are on a mountain bike it could be your neck that gets broken
P.S. Klein Rocks