The new 17 and 15-inch MacBook Pros with Core i5/i7 processors are fast. Fast. Overall I'd say they're about 50% faster than the last gen Core 2 Duos, which is about the same bump the iMacs got with Core i7.
Here are benchmarks to show exactly how much faster.
About 50% faster in the Geekbench tests.
The Xbench tests are a bit more all-over-the-place, but that's more because Xbench hasn't been updated in a while. Still, faster.
Re-encoding a file with Handbrake 64-bit shows pretty well the race between CPUs. At 19:54 vs. 32:19, the Core i7 MacBook pro—even though it's 2.66GHz vs. 2.8GHz—is just about 50% faster.
So there ya go, the Core i7 CPUs make a pretty damn big difference in performance. We'll be testing the Nvidia Geforce 330M discrete graphics in another post to see how much that has improved over the 9600M.