The 2011
MacBook Air with an i7 at 1.7 GHz is
1.6 times faster than the 2008
MacBook with a C2D at 2.4 GHz.
The SSD and the two extra virtual cores and the three year difference are probably the cause of that increase. Depending on your computational habits and needs, you might or might not see an increase. The extra pixel (1280 x 800 vs. 1440 x 900) might also be of benefit.
You could also just upgrade to an SSD with your
MacBook and see a very good performance increase.