That's a steal! Why's the old MacBook at an equivalent price? 100mhz doesn't justify that.
I recently upgraded from a 2.4 GHz macbook from last year to the 2.0 GHz macbook with nVidia graphics, I like it much better. I'm not sure if it's still on, but I bought it from microcenter because they had a $200 Mail in Rebate.
The general rule is that apple clears out its backstock of portables and ipods in the summer with its back to school special. It then introduces new models in the early fall in time for the holiday shopping season.