Amazon on Roku has a terrible UI. It can't suggest content well, it doesn't make it obvious what you've already watched, the descriptions are useless dribble which is surprising when Amazon owns IMDB. You watch a single kung-fu movie and your action movie suggestions get overwhelmed with kung-fu flicks. The separation between Prime and Amazon Video is easy once figured out in the app, but for casual users its a frustrating experience when the video they thought was included with prime is not.