Huh. I switched from FreeNAS to OpenMediaVault to avoid ZFS. The FreeNAS crowd seems to have no interest in supporting SOHO setups and simple and effective backups. When their SOHO offline backup solution is to build a second NAS, instead of just support USB, I left and didn't look back. OpenMediaVault does all the same things, but actually handles USB in a non-stupid manner, and has a more friendly community.
Yeah ... if I was needing a bigger storage device, I'd really want ZFS too. The downsides though are it needs significantly more RAM and CPU-power for a good sized ZFS installation.