I've got a Dell Vostro 1510 w/ Vista sitting in front of me, and coming out of sleep is "almost instant."
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.