Matthias Eckermann, the SUSE Enterprise Linux product manager, considers Btrfs ready to be officially supported by the German Linux company since the SUSE Linux Enterprise 11 SP2 release. Btrfs is officially supported along with EXT3, ReiserFS, XFS, and OCFS2. OpenSUSE continues to also support Btrfs file-systems during installation.
The SUSE Btrfs comments were made at Linux.com.
Outside of SUSE, Btrfs continues to be an install-time option for Fedora, Ubuntu, and other popular Linux distributions but no tier-one distribution has yet defaulted to the next-generation file-system over EXT3/EXT4. Meanwhile with upstream Btrfs, the btrfs-progs advanced this year and the Btrfs kernel code keeps getting new features.
For those wondering about the performance, from the imminent Linux 3.7 kernel I did XFS vs. EXT4 vs. Btrfs benchmarks.