[MCJ]

Let's be honest - the only way that Mac OS X is going to be truly competitive in the short-to-medium term with Windows / Vista is by Apple licensing its OS so that people will be able to use it on their Windows boxes. Technical issues aside this will not happen for two reasons:
- Apple does not want to alienate MS because losing Office: Mac will be a huge blow to the platform (free-ware alternatives notwithstanding).
- More importantly Mac sales would probably decline if people are able to run OS X on their bargain basement Dells.
In the long run though I believe that Apple's approach may be the right one. If open-source is the future the Mac OS with its Unix foundation is better placed to adapt to this transition than Windows in its current form is.