Upside: The future could mean running OS X won't require Apple hardware. In other words, the ability to run OS X on any Intel box. It also means that a huge body of people with existing Intel hardware will be able to use OS X.
Downside: I may never get a G5 Powerbook, but will have to wait for the G6 in 2006.
I'm reading between the lines here a little. But the news is very interesting.