Of Apple's three main transitions (the other two being PowerPC and Mac OS X), the switch to Intel has been going the smoothest. Just this week, we've seen Aperture 1.1, a new Firefox release, and an update to the WMV plug-in for QuickTime all arrive with Intel-native code. And via Boot Camp, Apple has opened its Intel-based computers to a few Windows programs that can take advantage of Intel processors as well. It's ironic, if not embarrassing, that the fastest version of Photoshop you can run on a MacBook Pro is available by booting into Windows, However, the path to a "Universal binary" when using Apple's development tools doesn't seem too rocky.
Prediction: Leopard may be a feline, but it will run like a dog on PowerPC.