Jobs was pretty much forced to pre-announce the Intel Mac if he wanted any third-party applications to be available for it by the time it was ready to ship. The PowerPC and Mac OS X transitions were also announced well in advance -- so, for that matter, was Copland, though it never happened. Had to be.

There are a lot of risks to the Intel transition. I think one of the greatest risks is that Microsoft will create a version of Virtual PC that runs Windows applications rootless at near-hardware speed, and stop producing Mac-specific versions of the Office applications. Once you're running Windows applications on your Mac, the Mac then needs to be a better Windows than Windows -- or else, why not just run Windows on the machine? There's opportunity here too, if Apple can indeed make the Mac a better environment for running Windows applications than Windows itself, but I think that'll be tough. Apple no longer has the UI lead it once had.