I understand this, the chips and their utilizations are different, but from my last generation desktop C2D to a current generation desktop i5, it gets smoked. Yes, it's quad core vs. dual core, but Apple never shipped a Mac with a Core2 Quad but they do ship the iMac with the same i5 750 processor I have in the Hackintosh. See here for performance differences between a 2.4C2D & the 2.6 i5:
http://www.electronista.com/articles/09/11/12/quad.core.imac.near.3x.faster.than.past.gen/
Everywhere you go though, the reviews show the i5/i7 line fly past the Core2 Products they're replacing, and when the Quad Cores enable Turbo Boost, they're even better. I can't imagine the mobile versions won't offer this kind of performance increase.
I'm an Apple aficionado, I love my Macs (the 24" iMac, the 3.06GHz MacBook Pro that I ordered and am waiting on and hoping is delayed because new product is coming out), but I just found it downright disgusting that for $800 I bought and built a computer that's running OS X flawlessly that just screams in power and performance, easily taking on the heaviest of tasks that I'd require a Mac Pro for. Here's to hoping that the MacBook Pro line gets these i5 & i7 chips soon.
In all honesty, I think the i5's should go for the 15" and possibly the 13"'s, and the i7's for the 17". BTO configs for the 15" can snag an i7, but I think it should go 13" = i3, 15" = i5 with i7 BTO on high end, and 17" with Quad Core i7. Seems perfect to me.