Just a couple of observations. Not trying to be negative, but just noticing some things.
1. Those fast loading apps are mostly Apple's. This is not a criticism of the test, just an observation. It shows that proper programming can yield wicked results. However, Adobe Elements and Safari show no evidence of actually launching. They may very well be hidden in the background somwhere, but I could find no evidence that they actually launched (other than the dock indicator, which is enough I guess).
2. Elsewhere on his site, he has the launch time of Elements as 6 seconds, which is nice, very nice, but not as instant as the other "Applets". I suspect full blown Photoshop, InDesign, Illustrator will still take several seconds each. Currently, Photoshop takes 18 seconds to launch for me on a DP 1 gig, so if I can get down around six seconds, that's quite a speed bump. I can live with waiting for Photoshop for a few seconds. What has always been really annoying is waiting for the little application-wanna-bes to load in multiple bounces. I mean, waiting more than one second for System Prefs/iTunes/Terminal/Calculator to open is a slap in the face. Not anymore.
3. I did a quick, super-lame, app launch test similar to his movie. I didn't bother to do a screen movie cap, so you'll just have to go with my info. My apps are mail/isync/safari/explorer/dvd player/itunes/iphoto/ical/omnigraffle/fetch/termianl/sysprefs. They appeared to launch in fifteen seconds, but actually they were still loading even though the dock bounce effect had stopped. Actual launch times were closer to 25-30 seconds. With the apps cached and relaunched, it took no more than 25 seconds to fully launch them all. I suspect this is why we don't see Adobe Elements and Safari fully loaded in the osxhints movie. Still, the G5 should launch apps very fast, I'm sure. To be fair, my understanding is that Panther is a big help in this area as well, it's possible that a DP G4 could launch those sames apps almost as fast.
4. MP3 rip. Rob states that he can rip MP3s on the G5 at up to 16.4 speed. My G4 DP 1 gig can easily match that. It easily breaks 20x speeds and has peaked at 25x. Average is around 15-17x. I presume he was ripping right from the CD, which means the SuperDrive is a bottleneck, so I can't fault the G5 for that. I'd be curious to see how fast it would rip aiffs from the hard drive (not that anybody would pull aiffs from the CD and THEN rip them, but often times I create AAC files from AIFs created in CuBase).
These are about as harsh of criticisms as I can muster, which means the G5 appears to be a monster.