re: all the negativity
It's not negativity, just bemusement

MorphOS 3.0 on a PowerMac G5 will be insanely fast, stupid fast! I will be hobby computing at the speed of light for a bargain price? I'm there.
Insanely fast at what, though? That's my whole point. What will you be doing with it where you can honestly say "wow, this is so much slicker and more responsive now that I have a G5" that isn't already on a G4 mac / Peg 2?
So far, we've seen HD playback suggested as an option. Ok, I am sure the G5 will play 1080p fine, but as I say, so will a dozen other systems that will cost you less.
Are there any amiga/mos applications out there that are just unusable on a G4 that I'm somehow unaware of?
If the motivation is simply "I just want to run MOS on the best, most powerful hardware it can run on", that's fine, I totally get it. But if the motivation is "I need a G5 because MOS on my G4 is too slow at X", then I don't get it, because I have no idea what 'X' is.
Is that any clearer?