Itty bitty 12" PowerBook G4. 1.5 GHz, 1.25 GB RAM. And.... drums... it DOES ROCK! Backed up to ext firewire hdd using SuperDuper. Did an Erase and Install of Leopard. Then used Migration Assistant to move everything back over. Took 2 hours to do the install and migration, then another hour to mess around with it until Leopard knew where everything is located at. Now, it just FLIES. It is just as fast as Tiger, maybe even a tad more snappy. No issues, no problems, no warning signs, no blue screens, no red or yellow exclamation marks... flawless.