Difference is 100Mhz on the processor (you have 1.3, the new ones are 1.4), which is negligible and makes 0 difference for 99.9% of people. Probably just changed it cause the old chips were running out and/or they wanted people to feel like they did more than just the $100 price drop.
Oh, yeah, and that, you paid $100 more for yours than it would cost today. But theres nothing you can do about that now so just enjoy your laptop.