DragonFlyBSD 3.6 brought major SMP/multi-threading improvements to its kernel, DPorts as the default package management solution, and Intel/AMD KMS graphics drivers. While the next DragonFlyBSD release is a ways out, Matthew Dillon has already committed some HAMMER2 improvements.
In February of last year it was shared that the HAMMER2 file-system was entering development, the successor to the HAMMER file-system currently used by this FreeBSD fork.
HAMMER2 is fundamentally different from HAMMER and uses a copy-on-block design and supports writable snapshots, multiple roots support, support for multiple compression algorithms, and other planned features. Matthew Dillon anticipated last year the file-system wouldn't be usable until sometime in 2013. Now we're almost into 2014, and HAMMER2 stabilization work and implementing promised features is still taking place.
With this DragonFlyBSD kernel commit on Tuesday there's a fresh round of stabilization work and improvements. Check out that link for the full listing of HAMMER2 file-system changes made.
It will be interesting to see how HAMMER2 compares to the other BSD operating systems in 2014 that are relying upon ZFS and then of course Linux distributions with Btrfs.