What do bears and hedgehogs have in common with my Thinkpad running Ubuntu ?

They can all hibernate !

I'd not tried hibernation since moving to Linux and, having had so many
problems with suspend/resume ( now sorted since New Year ), I assumed it
wouldn't work.

Oh, me of little faith.

I needed to switch batteries as I was running on empty - ordinarily, I'd
just shut down but, being brave, I hit the Hibernate button.

After 1-2 minutes of disk activity, the Thinkpad appeared to shut down
with all the LEDs being blacked out.

Having switched batteries, I hit the power button, entered my normal
power/disk passwords and saw the Ubuntu splash screen, again as per usual.

After another 1-2 minutes of disk activity, I was presented with the
lock screen, asking for a password, rather than the post-boot
user/password prompt.

Having entered my password, my desktop restored to where I'd left it,
with Notes, Skype, Twitux etc. all running, and the Lotusphere network
reconnected.

Not something I'd use every day ( I rarely did when using Windows ) but
much "cheaper" than a shutdown when power is low ...