I built a 6 disk TrueNAS Raid-Z2 box two years ago and though it was inconvenient to build vs buying something off the shelf, TrueNAS has been excellent. Does what it says on the tin and continually improving with each release.

Their cloud sync and UPS functionality have been great (flaky power around here). Haven't dug into the TrueNAS' ZFS pool/snapshot management and jails management (FreeBSD's containers) functionality, but both are compelling once I get time and a good project for them. The NAS performing so well has me itching to upgrade to 10 gigabit ethernet around the house once prices come down a bit.

Also I ran the OS off mirrored thumb drives until recently. That was pretty nifty.

I've been thinking about going down the TrueNAS route (the TrueNAS Mini series looks really nice), but it seems a little expensive. Is the extra cost worth the convenience of having a machine that you know will stay compatible with FreeNAS?