It's not unusable on my shield but it's definitely worse. Not just 'change is bad' worse, but actually worse.
Selecting a season and then the episode gives you the episode summary instead of just playing the episode.
Hitting back on an episode brings up a side menu sometimes and others it leaves the episode like it should.
Why Plex?
On my iOS devices, hitting a season and then the episode always took me to the episode detail. I'm not sure if this is a setting to configure, I never changed any plex settings other than setting direct play.
I don't have the "back" issue, there's an "X" on the iOS app to tap to exit the video, and the "menu" key on my Apple TV works as always.
So much for unifying the code bases! :D