This is kind of standard faire though. I did a `zpool upgrade` on my root pool once and broke GRUB's ability to boot my system, since there were features enable

This is kind of standard faire though. I did a `zpool upgrade` on my root pool once and broke GRUB's ability to boot my system, since there were features enabled that it didn't understand (wouldn't have hurt anything to ignore, but GRUB wants to play it safe obviously).