As a college student, I did a lot of research on the Macbooks, and waited for almost a year to get the new 2.4 Macbook.
I had decided on the 2.0 at first to save my parents $250. However, my awesome parents convinced me that the backlit keyboard would help a lot when I have to study in the dark library, during lectures, and when my roommate wants to sleep and I still have work to do.
Also, down the road, the extra 400 MHz might make a difference as I have to make this laptop last for 5 years. So for a long term investment, the 2.4 Macbook might be the best bet.