Originally posted by ESC:
The Celeron M does not have Speedstep so the battery performance is not as good as the Pentium M ("Centrino" if it comes with the integrated wireless). That said it's still a good choice as both are preferable over the Athlon laptops.
If anyone doesn't know what the speedstep is... Speedstep is on the Pentium M processors and allow the speed to "step" down to save battery. My 1.6GHz P-M drops to 800MHz when not under load. Also makes it run cooler... Only thing that heats up on mine is the 256MB Nvidia video card.
Another thing about the P-M's is they have a huge L2 cache, with my 1.6 having 2MB L2. Another thing I've heard is the newer P-M processor core is faster than P4 with the same clock speed. A review said the 2GHz P-M outperforms a non-HT P4. Another article I recently read on Toms Hardware is Intel may soon replace the P4 line with P-M based processors. Kinda like how 32-bit Athlons outperform P4s at the same clock speed (which is why AMD uses P-rating for them).
About the Centrino... A laptop is only labeled "Centrino" if you have 3 Intel parts:
P-M CPU (1.5-2.?GHz)
Intel 855 or Intel Mobile 915M chipsets
Intel 2100, 2100A, 2200BG, or 2915ABG mini pci wireless
If you swap out the wireless for a vendor card, you lose the "Centrino" label. Intel claims the combo of their CPU, chipset, and wireless maximizes the mobile computing experience 
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