A year and a half later and it's still chugging along quite happily. Now that the official FreeNAS 0.7 release is available I'm tempted to try upgrading, but I haven't come across any major bugs that affect me, so it's probably not worth the trouble.
Here's a look back at my disk space usage over the last year. If you recall, this is a 2 TB volume.
I will certainly run out of space before the end of 2010 if I don't start archiving or expand the storage pool. Unfortunately I haven't seen any good disk enclosures out there that support 4-5 drives over usb or esata. So I think I will be burning some dvd's here soon.