Everything that makes the Roku 2 and Roku 3 great streamers applies to the Roku 4. That's its biggest problem, too, but let's start with the good. 

Interface

The UI remains dead simple to navigate, with all its menus and apps neatly organized into rows and tiles. It presents apps instead of specific shows and movies (a la the Amazon Fire TV), which feels more straightforward. The overall aesthetic could use a refresh, but it doesn't take more than a minute to figure things out. Being able to sort the app grid as you see fit is still super convenient.

New to the OS is an improved "My Feed." This lets you bookmark your favorite movies, shows, and actors, who'll then appear in a separate tab in the main menu. You can then quickly access those programs from that tab instead of searching for them every time, and you'll get updates when your bookmarks have relevant new content.