Lots of reading about ZFS today. And a few experiments, too, doing snaphots, diffs, and scrubbings.
I really like ZFS, particularly that one is free to redesign filesystems long after they have been in use. ("Hey -- let's finally mirror this fs!"). There's so much more freedom compared to Linux-LVM.
(BTW, if you like ZFS, you'll like DragonFlyBSD's Hammer FS, too. That one even does nightly snapshots out of the box.)