The HAMMER filesystem has several features that put it on par with Sun's ZFS, such as maximum size of up to one exabyte, infinite snapshots, limited only by retention policy, streaming backups, asynchronous transactional support (no long fscks to check disk state), and much more. You can now also boot from a HAMMER-only disk, but for production systems the developers still recommend a small UFS
Version 2.2 comes in either a bare-bone CD iso, a fully-featured DVD iso with a configured X environment, or a small, 512MB bootable image for use on a USB stick. The release notes detail all the other improvements.
You can get this new release from the mirrors.