Regarding sremick's comments, if I were using FreeNAS in a serious server application where data integrity was a must, then I would absolutely invest in the proper hardware as he points out. If you read through any of the FreeNAS documentation, it clearly states what you should use and why.
I looked at the canned systems from Synology, QNAP, et al., and they can get expensive. I thought surely you could use a home PC as a simple (non-Windows OS) server. So I looked into it and everything I read pointed to FreeNAS. I thought I would see if I could make it work since I have all the hardware sitting around.
For me, FreeNAS does exactly what I need - fast, easy access to network stored data from all 4 home computers and I have $0 invested. Well, I did buy a new 3TB hdd, but I was going to buy that anyway as a backup hdd. So the way I keep the data sychronized between the hdd's of two separate systems (home PC and FreeNAS server), I am not too worried if the FreeNAS system (hardware) dies. I like the way FreeNAS works and I am becoming 'attached' to it (pun intended), so I may be willing to shell out some $ in the future for the proper hardware when the time comes.