I know a bunch of Windows-to-Mac developers who tell me they have to reboot their iMacs (OSX 10.5.2) every day due to software updates. I told them I dont believe them. They said they'll call me next time it happens. They haven't called me over yet.
How often do you reboot your Mac and why? Tell us what Mac and OS version you're using too.
EDIT: ps f*** dell for installing vista (but good on them for moving to linux) and super f*** ms for giving us this pos os.