We have learned, since the early days of Cheetah and Puma, that each new OS release is major bugware, so it's very unwise to replace a stable installation with a new OS. Always put the latest Mac bugware on a secondary disk or partition, and then wait a few months for the code monkeys to issue the dozens of patches needed to bring it up to speed. You might think that, if Jobs had waited as long as Bill has stalled Longhorn, there wouldn't be these problems. Unfortunately, in the modern world of unaccountable offshore programmers, what was once a speedy and orderly process, has now degenerated into a monstrous and impenetrable maze of conflicts to resolve with each new OS release. So the same problems will always occur, whether they dump a premature relase on the unsuspecting public, or whether they delay 3 or 4 years, through indecision over which features to copy from competing systems.