The whole problem with "well thought out" is that it's very limited in scope.
My story-
When I built my first FreeNAS box, it was a server. 8.0.4 was out and there was no timeline for when the "jail" functions would exist or how well it would work. All this newfangled "jail", "multiple jails", "encryption" and "ZFS v28" stuff was planned but had no timeline. My i3 could do anything I could throw at it. I could saturate all of its Gb LAN ports simultaneously while doing a scrub, etc. I thought I had a great FreeNAS server and there wasn't anything that my server couldn't do.
Then the jail function came out with 8.2. Once the jail came out my previously "overpowered" i3(don't taze be bro.. it was left over parts), while plenty powerful for a FreeNAS machine, suddenly needed more power if I wanted to run CPU intensive jail applications. SABNZBD, couch potato, and all that stuff come to mind.
Then we saw(and continue to see) people that get burned badly by not using ECC RAM. Again, my "horribly overpowered at the time of design" was shown to be falling short as there was no upgrade path to add ECC except a complete redesign.
Then, 8.3.0 came out and with it ZFS v28. While very nice to have it did cause a small slowdown in performance. I could no longer do a scrub AND saturate all Gb LAN ports with CIFS data at the same time.
Now 8.3.1 is out and with the geli encryption I have no need, but if I want to use that feature I either have a cripplingly slow system(CPU doesn't have AES-NI support) or I upgrade my whole server.
And the future..
-Well, there's the possibility that Plex Media Server will be able to run in a jail.. someday (transcoding needs lots of CPU power and I use Roku boxes which require everything to be transcoded). It could be this year, it could be next year, it could be never.
-9.1 is expected later this year and being the current latest version of FreeBSD is likely to see lots more plugins available for it(more CPU and potentially more RAM needed).
So now when I look back at my FreeNAS server I went from a "I got a darn good machine" to "Damn.. my server needs an upgrade" in just 16 months. Attempt to predict what your server's future needs will be is quite difficult, and spending lots of money may mean some upgradability, but it may also be upgradability you will never use.
Now, I have parts arriving today that will upgrade the FreeNAS server to have AES-NI support, will have 32GB of RAM, and has a e3-1240v2 ivy bridge CPU. I'm hoping to safely get ESXi running(yes.. there are backups) and hopefully this hardware will last me at least 3 years. I'm kind of expecting that my limitation in the future will be that "32GB of RAM won't be enough", but the upgrade from socket 1155 to 2011 to support the extra RAM is about $500(just for the motherboard and a slightly slower CPU). Mind you that plan is to support >32GB of RAM, not install it.
Heck, for all we know the FreeNAS project will close up shop next week, FreeNAS will suddenly be horribly unstable and not be usable anymore, or other nasty catastrophe and all this great stuff I'm spending money on may be for nothing. Not that I think the project is going to fail or FreeNAS is going to suddenly not be a great software package, but things can and do go horribly wrong. Sometimes without warning.