ZFS is still a second-class citizen in the Linux ecosystem.
I'm still not sure who to believe. On one side they claim it's due to the license and fear of being sued by Oracle. On the other side they say it's due to Torvalds' "not invented here" attitude.
Either way, it kind of sucks that ZFS essentially "duct tapes" itself to Linux kernel development.
(I've read on other forums people locking themselves out of there own Linux system, being unable to boot into their OS installed on a ZFS root, even after months of success.)