Obligatory note that unless you have a good grasp of how TrueNAS works under the hood, and are willing to put up with sudden breaking changes, you should not be running the nightlies.
You will get virtually zero support on the forums, as barely anyone actually runs them. I run them exclusively in VMs when testing code changes but would never personally daily-drive (nightly-drive?) a nightly build on my main system.
Obligatory response: As my profile states, I’m an ex Sun Microsystems engineer. TrueNAS is based on mature releases of Linux, ZFS, and SMB so even with the nightlies there’s little risk of file sharing breaking or data loss (and I have backups). I just like playing with the latest bits like WebShare and TrueSearch. I’ll be moving to ZFS AnyRAID as soon as it’s available.