We use btrfs in production on thousands of nodes, and we make use of advanced features (nested snapshots, seed device snapshots, etc.) It has performed admirably so far, with only one problem attributable to btrfs itself (seed device incompatibility with device pools, seen in 3.2.0).

It may not have RAID 5/6, or time-proven stability, but it kicks ass and over time it will kick ZFS's ass not on technical grounds, but simply because ZFS has too much baggage and not enough community support.