I have never even tried to hibernate my PC - I always close/reboot - so this is fantastic to me.
It's great if you have 2gigs of RAM... it's OK if you've got 4... above that, hibernation starts taking a bit too much time for my liking.
But on a developer laptop running heavy
Adobe CQ5, the accompanying CRXDE "lite", a zillion chrome tabs, a few firefox and IE windows, a bunch of console windows, text editors, and... all that jazz... well, trust me, hibernation is a love affair. About a minute to boot into a fully-working desktop, or ~15min to start up all the crap from a cold boot? Geeh, let me see...
The win8 "hibernate just the core" idea seems interesting, but dunno how much it's going to matter - the Windows boot sequence doesn't seem to take a lot of time compared to POST and post-boot-load-all-the-startup-crap on most systems I've dealt with.