Curious if snapshots can protect you even as far as OS upgrades gone wrong. I'd assume they can, if all filesystems are ZFS + snapshotted.
My issue was that for some reason Linux no longer could find the encrypted partition to decrypt, so I couldn't get it up to a point where I could even work with it.
Your experience has definitely not discouraged me from wanting to ZFS my root partitions though. If only to provide the potential / theoretical ability to roll back a snapshot if necessary!
I can post my "script" when I get home if you want to try it. I use script very liberally, it was my notes of the commands I used in order in order to get ZFS/dmcrypt working.