i have a developer kit with leopard ... i've looked at zfs ... its a piece of crap ... its only an option on DiskUtility ... no GUI management tools; the man pages are incomplete; i tried 3x to copy to a pair of disks (which i formatted using the pain in the butt command line), and 3x it hard crashed my system requiring a reinstall of the os .... ymmv, but i suspect this is a turd wrapped in a cream puff, i just don't understand what the excitement is about.