I gotta say that FreeNAS, although version 0.69, works flawlessly for me.
FreeNAS has been a webserver, ftp server, torrent client, picture library, Xbox 360 media portal (with automatic transcoding), music server (could also serve as Itunes server), file server and backup server for more than 4 years now. And all that on a Pentium III machine with 256Megabytes of RAM. Energy saving settings reduce the power consumption.
The machine emails me when something is wrong (temperature, disk full, illegal access, etc) and has been rebooted about 10 times in those four years. All were because i wanted it to reboot.