I've been using hibernation on Windows 7 since I've have it, and it's been rock solid. Recently I got a new laptop with a couple of SSDs in a RAID-0 configuration and have installed Windows 7 on it.
What I'm finding is that normal shutdown and restart are fine, however when I hibernate, the PC boots up and then reports that it can't find the disk.
It only happens on hibernation. If I hit
Ctrl-Alt-Del again a couple of times it's fine.