Do you know what price they generally run? I looked at some bikes at Dick's Sporting Goods yesterday, but I don't know enough to tell the difference between the $150 and $450 models. Are there absolute certain features I should be checking for?
You should be looking for at least 100mm of front suspension, a double butted aluminum frame, and Shimano Deore components at a minimum. You want to avoid cheaper straight guage frames because the bicycle will be extremely heavy by comparison, and you want to avoid the lower end 7 and 8 speed (21 and 24 total gears respectively) drive trains in favor of the better 9 speed (27 total gears) speed drive trains.