Is DDR3 RAM really worth it over DDR2?

I am thinking of getting a new motherboard, and am wondering if I should splurge on something that supports DDR3 or just stick with DDR2 capabilities. I really don't know a lot about the subject. Is DDR2 going to be obsolete or poor or something? Actually, how much better IS DDR3 over 2? If you could explain that would be greatly appreciated, thanks.