I found this cool video on YouTube via Digg this morning. They simultaneously boot an iMac G5 and a new Core Duo iMac to see which is faster at booting. The Core Duo, of course, leaves the G5 flailing in the dust, but I, along with many of the commenters on Digg, am suspicious of the state of that iMac G5. It really shouldn't hang on boot for as long as it does. During the video, one of the guys says that the iMac G5 had been through its initial boot and then was immediately shut down, so I wonder if they forced it to shut down and some of the disk check processes are running and slowing things up.
In any case, despite all these academic arguments, if you watch the video and you've ever seen an iMac G5 boot before, you're still going to realize that the Core Duo is absolutely smokingly fast.