I don't think I have seen this posted anywhere else, but here is a bit of trivia about the operation of the power light on the iMac G5.
Apple have changed the operation of the power light from previous iMacs, the new G5 now does the following :-
When the iMac is on and in use - Power Light is off, nothing can be seen.
When the iMac screen has been powered down via the Energy Saver setting (the machine is not asleep, just the screen) - The Power Light is on full and steady, this is new.
When the iMac is asleep - The Power light pulses, but blends from fully on to totally off, not just a partial fade up and down as in previous models.
Jut thought the Apple trivia fans might like to know this.
Ian