I couldn't find all the numbers for any 2007 mainstream notebook cpu, but here is a comparison between 3720QM (an upper mainstream, 2012) and P8400 (upper mainstream 2008):
Model 3DMark06 CPU Cinebench R10 32Bit Single Cinebench R10 32Bit Multi SuperPI 1M* SuperPI 32M* wPrime 32
3720QM 6470 4810.5 16822 11 594 12.9
P8400 2014 2526.9 4700.6 22.1 1212 34.2
321% 190% 358% 50% 49% 38%
So you would see 2x performance in single threaded, 4x performance in multithreaded and probably way better battery life due to stuff like TurboBoost (and getting a new battery :-)