Anchor, an Australian web-hosting company, shared their findings after doing extensive research and testing of Btrfs. Overall, the Btrfs experience was "very positive" but they ran into regular issues with hung tasks during snapshotting, a bug causing CPU soft lock-ups, problems when filling up a Btrfs file-system, and some other shortcomings.
Positive findings include good use by staff on workstations and personal servers, Btrfs in conjunction with Ceph, zero data loss or corruption thus far, very good data integrity, and can be used for managing thousands of snapshots.
The hosting company decided to stick with EXT4 for now but they will continue monitoring ZFS and Btrfs. Their findings in full on Btrfs can be found on the Anchor blog.