The M processor is faster then a standard processor running at the same GHz by a long shot.
Remember the fastest, most powerful computer in the world are Sun Sparcstations and these only run 1.28GHz. It's a different architecture, same goes for the Centrino chip. It is slower then a P4 in GHz but processes information more efficiently then a P4.
It is also scaled down to meet the needs of a laptop. Scaled down, I mean a regular P4 chip has a lot stuff in there to support a number of applications from being used a server to CAD workstation to gaming. While the Centrino chip is scaled down to support only items required on a laptop. Another reason it is scaled down is to conserve energy and help manage energy. Plus laptop are not gaming or server demaned, so having all of the power is not necessary.
Also for you AMD freaks. Is an AMD chip just as fast as a Pentium, based on GHz alone?...not even close. Because the fastest P4 runs at 3.40GHz while the AMD only runs at 2.4GHz (64 FX-53). And why does AMD market their processors such as XP 3200+ or 64 3400? Because people don't understand speed of a processor. Which one would you rather buy an Intel Pentium 4 at 3.40GHz or an AMD XP 2.20GHz processor? Hint...they run at approximately the speed exact speed. That is why AMD markets the XP 2.2GHz chip as the Athlon XP 3400+ so it doesn't lose sales to Intel for a similar processor.
So don't be quick to judge a processor by the GHz speed.