Neither can I.
Tuesday afternoon: Received MacBook Pro.
Tuesday night: Charged MacBook Pro, gave it just enough of an exam to be sure it functions.
Wednesday, 9:00 AM: Fire up Migration Assistant to transfuse my life from my PowerBook G4 to my new MacBook Pro. It failed because I set up a user ID on the MacBook Pro with the same name as my the main ID on my PowerBook. There are lots of ways to finesse this, but I took it as an opportunity to do a clean install.
Wednesday, 9:35 AM: The install finishes. I reboot and use the install-time migration to pull everything over from the PowerBook.
Wednesday, 9:36 AM: The migration says it'll take four hours and I have to be at the airport in two hours. I let it run anyway; what can it hurt?
Wednesday, 11:15: The migration is finished, 60 GB of data transferred with just two irrelevant warnings.
Wednesday, 12:50: I open the MacBook Pro in flight and start working. I find that my MacBook Pro, post-migration, is a functional clone of my PowerBook G4. All of the PPC apps I've used so far run. They're noticeably slower and they drain the battery faster, but the apps run without errors. I am 100 percent back in business.
Now it's Thursday, and I've had a full workday with MacBook Pro in my lap. Two days is too soon to declare a successful migration. The PowerBook G4 is right here as a backup. But the early results are very encouraging.