Just got done flipping through the MacBook Pro user manual over at
Apple's site, and one big change caught my eye regarding the powerup and shutdown sequence:
Sleep indicator light
Pulsates when the MacBook Pro is in sleep mode. The white light glows steadily for a short
time when you start up and shut down your MacBook Pro or when the display goes dark
to save energy.
This should be helpful, since at times I haven't been sure if my Powerbook was booting or not. If the startup sound is muted, you really have no way of telling the system is booting until 10 seconds in when the screen powers on, unless it is quiet enough to hear the hard drive.