I have an old Poweredge R520 rack server for NAS duty and CCTV. Not tried trueNAS personally, and currently run unraid. It has a couple of shares, and CCTV running via a docker.
Good: Has been fairly hassle free to get up and running, and reliable. I like that it spins down drives.
Bad: I notice the poor write speeds ... when I write to it, i tend to write large volumes of data which blows out the cache, and then drops to sub 50Mb/s write speeds.
Prior to that, I was running Ubuntu server and ZFS shares ... and I'd say it was markedly faster in its writes.
Although I paid for the license, I am still considering switching back / trying something else.