I've noticed since I got my new MacBook Pro (6,2, 10.6.7) that when the battery runs out while the computer is sleeping, Safe Sleep doesn't kick in upon restart. It used to be that with my old MacBook Pro (3,1, 10.5.8), when the battery ran out while the computer was sleeping, I would get the progress bar under the Apple logo during EFI boot. On my new computer, when the battery dies, the computer dies.
When I put the computer to sleep, there is the delay before the breathing light comes on (as it's writing the contents of memory to disk for Safe Sleep), but it seems to make absolutely no difference when I turn the computer on. Any ideas?
Edit: As suggested by @Chris_O:
perfora:~ tyson$ pmset -g | grep hibernate hibernatefile /var/vm/sleepimage hibernatemode 3