Some of the new features are:
1. Stability - more mature ZFS code, comparable to Solaris 10 update 8 with latest bugfixes
2. Compatibility - Solaris 10 update 8 default ZFS pools can now be imported into FreeBSD
3. Features - user and group quotas (ZFS-internal) are very useful for intranet fileservers that want to use ZFS
4. Speed - a 15-20% RPS yield in PHP webserver workloads with codebase on ZFS
The full commit log contains a list of Solaris updates applied to the code.
Though the current ZFS version is somewhere in mid 20-ies, I'm completely siding with the crowd which would rather have a stable ZFS than a more flashy ZFS.
The new code (ZFS v15) will first appear in FreeBSD 8.2 and/or 9.0 releases.