I installed Solaris 2008.05 on my laptop a short while ago. Being my usual goofy self I was playing around as root in places I shouldn't have been and managed to really mess things up and render my machine totally unbootable. It was nosediving within a small fraction of a second after booting... I only had one kernel image, and that file had been overwritten :-( Ending up in an infinite reboot loop. In past days, with either Linux or Solaris, I'd have reinstalled the system, possibly preceded by ripping the disk out and plugging it into another machine so that I could rescue any important files. But since 2008.05 uses ZFS for everything - even the root filesystem, all I had to do was boot the 2008.05 LiveCD, zfs rollback the root filesystem, and like magic all my screwing around was undone.