It has been a while but Plex has finally come to the Apple TV. With the new Apple TV supporting an app store Plex have an official version available, there were workarounds in the past to get Plex on an Apple TV but they involved Jailbreaking or DNS hacks but now that is a thing of the past. The new app is free and you need the latest version of the Plex Media Server for it to work and it supports all the usual Plex features like movie, TV and music playback. I have to say the user interface looks great.
The great thing with Plex is that they have clients for Windows, Android, Roku, Xbox and more so you have plenty of options for consuming your media.