The most obvious new "wow" feature: the pricier MacBooks are built using Apple's new "unibody" manufacturing process, where they essentially make them out of one "brick" of aluminum. (The $999 MacBook is made of polycarbonate, a very tough plastic.) With this process, Apple is claiming that it can make a beefier computer that, nevertheless, is thinner and lighter -- but don't take my word for it. Check out the official specifications here. They're using the same process for the MacBook Air, that super-thin laptop they debuted several months ago.