You don't need Plex folks. Ever heard of iTunes Home Sharing?
Store everything on your Mac or PC, (including externally attached hard drive), and then log into iTunes on your Apple TV, and turn on Home Sharing.
Besides, if you want to access your content on the go, I would rather bring my external hard drive with me to my friend's house (or my Mac or PC) and just airplay it.
You don't need it, and frankly, I'm glad Apple fixed this loophole, because it can become a security risk in the long run. (there is a way to exploit this and allow some thief to log your iTunes password, and then using that, to rack up lots of iTunes purchases.