i have been using btrfs in production for years now and it has never failed me, and i am doing hundreds of snapshots and send/receiving, i've reconfigured raids on the fly and went from 6 disk raid 10 of mixed size to raid 10 of same size. we have in some cases had many power failures with no data loss. We also have some set up using md raid and some using hardware raid...
when i hear people dogging btrfs it just speaks to their inexperience imo.
Raid5 and 6 are unstable in the "avoid at all costs" kind of way.
This may be of use if youd like to know more: https://btrfs.wiki.kernel.org/index.php/Status