Centrino mobile technology allows the processors to use less energy but provide fast processing speeds. Centrino chips also have a whoppign 2mb internal cache which increases processor speeds greatly. Although mobile P4s run at faster clock speeds (2.8, 3 Ghz, etc.) laptops that use these chips generally are bulkier and consume the battery faster. If i were you I'd wait until the end of Jan '05 before purchasing a laptop with a centrino chip. The current ones range from 1.5 to 2.0 Ghz running at 400mhz front side bus. Mid-January, intel's coming out with faster centrino chips with 533mhz FSB. In lamen terms, laptops with this new chip will be really fast.
As far as which laptop to get, i'd do some research online and at the stores. Several people have mentioned Toshibas, and yes they are nice. You should also check out IBM Thinkpads. I have the T42 model. Let me tell you, this thing is built like a tank. Features that make this laptop stand out include the following: internals fully encased in a manesium alloy case, solid metal hinges(other companies use a metal rod attaching plastic parts), keyboard with excellent tactile response (not mushy like lots of notebooks out there), gigabit ethernet, antenna along the LCD screen for excellent wireless reception, hard drives that protects itself when the laptop is jolted or falls, and much more.
I hope this info helps you.