Rebooting from the menu is handy if you e.g. flash the kernel, and then wish to reboot; a little quicker than shutting it down, waiting, and then holding the button for 2 seconds to power back up.

Soft Poweroff is rather broken in current OS2008, but fixed in Diablo. It lets you have the lights go out, screen and keys locked, and optionally disable radios (either always or only when no active connections exist), and then bring it out with a single power-key press. It's quite nice.