For most of these content channels--sorry, Roku, it's the best word here--the experience is similar, if not exactly the same, as it was under Apple TV 4.4.4. However, the Movies and TV Shows items have each lost their home-screen menu of options, with each menu item leading to a different screen. Instead, each of these two channels has combined its various screens into a single one, with the menu of options--Purchased, Top, Wish List, Genius, Genres, Networks (for TV shows), and Search--across the top of the screen. This makes it easier to switch between options, as you no longer have to back out of, say, the Top Movies screen to get to the Search screen; instead, you just scroll to the top of the screen and select Search. Selecting an item from this horizontal menu, or scrolling down the Movies or TV Shows screen, hides the menu; pressing Menu or scrolling back to the top of the screen displays it again.
The new interface is already inspiring debate among users--I've seen plenty of online praise and complaints. But overall, I think it's an improvement, as it makes particular content easier to find--you don't have to remember which top-level menu hosts the content you want to access--and it makes previously buried content more discoverable. (Didn't realize the Wall Street Journal has its own video channel on the Apple TV? Now you can't miss it. And my family loves that Radio is now a top-level item.) And when viewing the home screen, a down-arrow press hides the poster row to show just the 18 content icons. In fact, my biggest complaint is that whenever you return to the home screen, the poster/image area at the top of the screen is visible. I'd prefer to always see the all-icon view.
I also find that the new interface makes using the Apple Remote--one of the Apple TV's biggest weaknesses--a slightly better experience, thanks to the large icons and reduced menu navigation. And a change that appeared in a previous version of the Apple TV software is just as useful now: Pressing and holding the Menu button at any time takes you all the way back to the home (top-level) screen, saving you from having to press Menu, Menu, Menu, Menu when you're deep in a particular menu branch.
Opening the door?
Of course, one look at the new iOS-home-screen-like layout, and your mind starts imagining other icons--like, say, one for Hulu, and another for HBO--filling up spaces in the grid. Indeed, this new UI seems to me like an obvious first step towards allowing content-provider-specific apps, as well as perhaps other types of apps.