Quickly: After watching the keynote it looks like this transition will go insanely smooth. Universal Binary says it all. And in grand Apple style they make it as simple as clicking a checkbox for developers to make the switch to new hardware. This will be nothing like going from OS 9 to OS X. Rosetta is perhaps the biggest head-raiser of all. Where did this technology come from? Born from Apple alone? Transitive Corporation? It looks pretty fast from the keynote footage. This will create much speculation until Apple spills a little more info.
It was interesting to hear the Intel CEO talk about Intel chips getting cooler. Just this weekend I put together a P4 system for my brother, and that thing is HOT. The monster fan that accompanies the chip is terribly loud. It will be interesting to see how Apple and Intel address the heat issue.
The biggest downside to the switch to Intel will be the forthcoming pirated copies of OS X that will be running on every script kiddie's Dell machine in the coming year. Apple will continue to only allow OS X to run on Apple machines(via OpenFirmware, some special ROM chip, etc.) but this will be cracked, and I predict very quickly. (Perhaps this was one reason behind the much-hyped Tiger Leak Lawsuits?)
There was a lot of speculation that Intel would be making a custom x86 chip for Apple alone, but this doesn't seem to be the case.
The switch to Intel opens the door VERY WIDE for a WINE type app to be integrated into OS X that lets Windows users run most of their favorite Windows programs on their brand-new Macintosh.
Quick notes: The guys from Wolfram Research were superb in their presentation.
What the hell was M$ thinking with their MacBU spokesperson? She looked like Gates in drag, and sounded even worse. While many expected a switch to Intel, I don't think anyone expected a potential transition to be so smooth and so soon. Jobs eluded to upcoming PPC products multiple times. What will they be?