As I said before. It depends on your needs. freeNAS can be used for production environments and the underlying system is by design "induastrial grade" in terms of security (freeBSD - linux, unix and all those base more or less on that OS design pattern), redundancy (zfs file system with error detection / correction, raid1, raidz, raidz2, raidz3, duplicated copies of a single file, remote sync to offsite storage, snapshots to rollback changes, massive volumes spanning tons of drives - zetabyte file system!). This is developed for very large data-center and not mainly for home use video libraries.
Because it is now open source any one has access to this high-tech stuff, and yes - you can store media files on it. But it is much more than just a tiny cheap consumer NAS. Giving it the right hardware you can run serious business on it. iSCSI, link aggregation and thos stuff is also very unlikely to be found in consumer setups - it is more data center - server cluster gear.