i also administer a freenas box for a small business and this stuff is rock solid, i would only wish a _easy_ solution to get the permission stuff right in a multi user setting.
none the less, thumbs up for creating this, cool stuff!
Also, the fsck tool is still very immature. It takes many years to get good at detecting and recovering from corruption.
Be prepared to update your kernels and tools often and independent of your vendor. Btrfs-progs will likely need to come from the git repo, so building your own packages for distribution around your production nodes will probably be necessary too.
A word of caution: do not run btrfsck without consulting the wiki and mailing list first, and hopefully knowing exactly what you are doing. There are situations you'll encounter which do not require btrfsck to repair (but rather, other tools instead), and it will potentially make a recovery less likely.
FWIW, I have been watching the list for years, and reading regularly for about 6 months trying to get a sense of stability with respect to the features I want.
I would not put btrfs in production yet. Though, likely soon.. I'd guess another year or so.
New kernels should be no problem as Ubuntu will likely provide an HWE stack in the future and btrfs-tools is inside a well maintained ppa...
Damn' I should have pushed ZoL through.
I have been waiting and watching for a long time for most of these "new" filesystem features (pools, fs-level RAID, checksums, send/receive), but I am a "filesystem conservative" (especially in production; less so on my own machines) -- I'll keep waiting awhile longer. On production Linux today, I stay with EXT4 or XFS.
Can you elaborate on the permission-stuff issue you have? We'd love to get it right in Rockstor.
Can't remove raidz's from zpools, but `btrfs device delete` exists.