Unless I'm mistaken, Plex is using the 2D API. I believe Crackle is using the NDK, which would explain why its fancy version is only available on the Roku 2 and 3 (lower end boxes still have the old grid screen UI).
I'd imagine developing something like the new Plex channel would be much easier using the new SceneGraph framework, so I'd personally go that route.
My Channels: http://roku.permanence.com - Twitter: @TheEndlessDev
Instant Watch Browser (NetflixIWB), Aquarium Screensaver (AQUARIUM), Clever Clocks Screensaver (CLEVERCLOCKS), iTunes Podcasts (ITPC), My Channels (MYCHANNELS)
