I'm planning to pick up a new Macbook tonight, but can't decide between the 2.0GHz and 2.4GHz models. Is it worth $300 to get the 2.4? I don't think I really need a backlit keyboard. I can always upgrade the hard drive at a later time. I really just need something to carry around. It's not going to be my main computer. I have an iMac at home. The Macbook will be for travel. Is there a major performance difference between the 2 models? I guess that's what it comes down to.