For what it's worth, I've had very good luck with zfs-on-linux on my 12.04 system. Multiple pools, largest is 20TB. Zero problems after a year of use. Switched from mdadm/xfs due to major data loss from corruption, and I don't plan on looking back.
I have a NAS that uses mdadm now (it did save me when one disk went completely bust), but RAIDZ sounds even better.