cross compiling mac ports and intel vs. PPC architecture

I too just received my shiny new Mac Book Pro today and am upgrading from a Powerbook G4 as well. I used Apple's "firewire upgrade method" where I connected my old laptop to my new one with a firewire cable and it automagically sucked everything over. It worked amazingly well. Everything works. I expected broken binaries and heartache but it all "just works" including all my ports. I assume my ports are running with that Rosetta translation module. Will they run faster if I do a clean re-compile? I wonder if there might be some way to add an option to similar to selfupdate that is a an"arch-migrate" target that recompiles all targets for the new architecture. David