Might be between the keyboard and chair issue.
I have Backuped my boot disk from my powerbook to an external drive and have made it bootable. I then connect my external drive to my iMac and boot off of the new image. Works great. Before I leave, I do a "quicksync" and I am good to go.
I have found a couple interesting issues though. When I boot of the drive, I can no longer print, and my iTunes/iPod started saying that my computer is not authorized.
I haven't found any other interesting stuff, but was curious if people have seen this, and if there was a workaround.