Yes, Vista doesn't, IIRC... at least I can't find it
I want it back
Start menu -> little arrow next to the two buttons which turn off and lock respectively (bottom right) -> hibernate.
I don't have it.
I'm assuming it's an Ultimate thing... I never used to reboot before, just hibernate
I have a button to the left of the Lock button, which "saves my session and puts my computer in a low power state so that I can quickly resume working." Hibernate, in other words.
You can also change your settings in Control Panel > Power Options > System Settings to make your PC's or keyboard's buttons engage hibernation(, sleep, or shutdown).
That's in every edtion of Vista I have used thus far (Home Premium, Business, Enterprise, Ultimate).