MacBooks made the move to Core 2 Duo today. Apple cites only a 25% performance upgrade compared to the 39% performance upgrade of the newly updated MacBook Pro's.
I'll have to check the specs to see why.
UPDATE: Yes, it appears that Apple is once again widening the gap between the Pro and Consumer lines. The MacBook Core 2 Duo revision maintains the clock speeds of its predecessor, while the MacBook Pro line has gotten speed bumps.