I love my Apple TVs (I have three of them), but it's increasingly frustrating that I have to sync my content to iPhones and iPads. I have an old 2009 MacBook Pro with a 1 TB hard drive that serves as the hub for my Apple TVs. Unfortunately, this is not the computer that my iPad and iPhone sync with. If I want to sync one of those movies to my iPad, I have to share it via AirDrop or Dropbox. I then add it to iTunes (and then sync via lighting cable).
Plex is a media application for the Mac, PC, and various NAS devices that has a corresponding application for Roku, iPad, iPhone, etc. It's dead simple to install and get working. It's a simple web server that you install (you drag the file to the Applications folder and run it to set up). It then runs in your menu bar. I told Plex where my movies and TV shows were located and it went to work scanning them. I am meticulous when it comes to metadata, but Plex does the heavy lifting if you aren't. Through the free Myplex service, it's simple to share to your iOS devices when you are on a different network (WiFi or cellular). It's even possible to share your library to another Plex user (to their Roku, iPad, etc). With the optional PlexPass, you can even download movies or TV shows for offline viewing (PlexSync). The PlexSync feature is free for PlexPass users during the beta period, but will be an optional subscription afterwards. The folks at Plex have not said how much it will be or whether a PlexPass will be required or not.
The great thing about Plex is that it doesn't interfere with my Apple TV. I still use iTunes to manage my media and therefore the Apple TV can see it just as before. The only difference is that Plex is watching the movie and TV show folders in Finder. The main downside of Plex is that you must leave a Mac/PC running at all times. I'd love a service like iTunes Match where it could scan my library and serve it up via the cloud. In the meantime, Plex will give me a nice solution. I was already leaving a Mac on to serve up Apple TV content and now I can use it wherever I am (with no syncing via lightning cable).
Plex for Apple TV - I don't use this, but it looks interesting.