I know plenty of people are happy with Windows 7 and Vista but with me Windows has such a bad history of crashing/hanging while coming out of sleep/hibernation that I can't trust it.
My boss' Vostro was inexplicably hanging on logout/login, that seems to have corrected itself after a few forced reboots. (And I've had that experience a few times on all OS's, including OS X.) Actually, I can't remember it for Linux, but Ubuntu is much less careful about shutting down gracefully than Mac/Windows.
* I've had four failures to wake from sleep due to low battery in a 2 month span I was dealing with an old battery that was failing.