I went a bit overboard in buying one, but I'm really liking it now. I bought a DS1512+ and five 3TB hard drives for about $1600. So far, it's been great. It was a breeze to setup, it's using a hybrid RAID format that's expandable, and I've got an FTP running on it now. Using iSCSI to be able to map drives on my computer for apps that don't support network locations (hey Steam) is awesome.
I'd highly recommend it.