I am running ~30 of them in various ZFS configurations. 16 of them are running in FreeNAS.
Its not clear if they are PMR or SMR. There are mixed reports and frankly they don't quite act like either. Perhaps some sort of hybrid (we know Seagate uses hybrid PMR/SMR on large 3.5" drives).
They work fine in a ZFS RaidZ/RaidZ2 pool under FreeNAS. Slow - but fine. They read reasonably fast but don't seek worth cr@p. If you want them for backups or a media pool to feed your Kodi/Plex then they are all good - in fact really good. If you want them for active work they might not be the best. If you are serving more than a 3 or 4 user community from FreeNAS then probably not. Probably wouldn't try to use them for VM images.
As for reliability I've had one soft-fail out of 30 in about 8 months, and it failed within about 30 days (infant mortality). This actually makes them among the more reliable spinny disks i've used.