
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.
DISCUSSION
my favorite things about these machines are the monitor, the amazing magsafe charger, the keyboard and the aluminum body. why can't someone make a windows machine with these specs? they would sell like hot cakes, no probably better than hot cakes