The first thing that catches your eye in the app that it is virtually useless as long as one does not possess a "PlexPass" or the app unlocks for about 4. Okay, 4 are not dramatic, and I have also paid. Now the app seems however to have an error that they forget the simple activation and take. Then you can either pay again, or you delete the app, reboot and reinstall again. Then it's back for a while.
Otherwise, the server seems to have a bug. I can not play media on SD because Plex think is having to recode my mp4 / h264 files. But I'm pretty sure that the FireTV that should actually be able to play natively.
All in all, more of a disappointment.