FreeNAS suited really well in managing our legacy systems and it handled all our network flows really well, less maintenance is required on our part. FreeNAS also gave the option to switch to TrueNAS for free as now its support is limited. The major issue that we faced was with the installation as it is really complex and required lots of time. Rest all is good and FreeNAS still works well on our systems.
Before swapping to FreeNAS, we'd been using plan old Linux servers running Samba and NFS with ZFS storage underneath. This worked really well for our requirements at the time but required a lot of administration when new versions came along, or new users had to be added or drives needed replacing, and so on. FreeNAS did away with 95% of that work and does a much better job too.