Netflix is an HTML 5 app that uses a custom web engine that they designed themselves and utilizes the Roku NDK, which is not available to non-partners. It does not use standard Roku components. You can accomplish a similar look and feel with the 2D API if you're willing to put in the time, but to say that it's a lot of work would be an understatement.
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)