I have MBP and it runs about the same speed as my PB did so its an upgrade in a sense once the UB is available. I do also have windows on here also which AE/Flash run native and its really quick. So either dualboot and run AE natively on windows, or run AE in OSX which will run about the same speed as a PB.
model – 15″ 2.1ghz / 1gb ram
Phife