Norman Richards asks Why wait for Intel?. He argues that you might as well upgrade now if you want a faster Mac. I've had a very personal experience with a new Mac recently and I don't think it's worth the upgrade. My "normal" PowerBook is a 17" 1.33 GHz with 1 GB RAM. The new one I bought is a 17" with 1.67 GHz and 1.5 GB RAM. When I first got the new PowerBook, I did some brief tests against my current benchmarks. To my surprise, the new PowerBook is not faster than the old one. In fact, in some tests it was slower.
Yes, this does seem impossible. I will re-run these tests before I get rid of this new machine, but right now I don't see any reason to upgrade.