As someone who uses FreeNAS and who has many customers running it in high demand environments, I'm going to have to disagree with you.
Speaks more of your lack of experience than FreeNAS itself.
FreeNAS has felt kludgy and broken for years now. Perhaps just because you work with even shittier and ridiculously expensive NetApp crap, you think that FreeNAS is impressive, but its really not.
I dropped FreeNAS some time ago, its ZFS support (due to using old releases of FBSD) was asstastic, and as such, performance was absolutely pathetic. Unless they've bumped up to AT LEAST 9.1-STABLE, ZFS performance is still going to be asstastic, forget about how shitty the UI is for it.
In the end, you're better off just using a bare install of FBSD and the CLI to setup a NAS. Using it for replacing high end NetApp gear? No fucking way.
Note: All my NAS equipment is FreeBSD based now, none of it is FreeNAS.
Great idea, shitty shitty shitty implementation.
JKH on the other hand, is one person I trust to make it not suck anymore.