The *really* interesting thing about Centrino isn't the WiFi chip integration (which is just band-waggoning - been there, done that), but the fact that Intel, in their own ads, states that the laptops powered by the 1.6 GHz Centrino chip will "outperform" 2.4 GHz Pentium 4 Mobility chips! Megahertz myth....
Apple has a great opportunity to "de-ride" the Centrino hype. Apple G3/G4 laptops have had a significant portable performance advantage over leaden PC laptops (unlike the desktops). Finally, Centrino is playing some catch-up (in 802.11b support, battery life and actual performance).