Netflix have updated the Windows Phone version of the app. This update adds support for hi-res Windows Phone devices like the HTC Windows Phone 8X. Version 184.108.40.206 fills the screen on playback and has got rid of the black bars that where present on the previous version. The 8X runs at 1280×720 so natvie 720p playback looks much better. Nokia’s Lumia 920 runs at 1280×768 which matches the aspect ratio of lower screen resolution of older devices running 800×480 so you don’t get black bars on that device.
The release notes don’t have any details on what else is new with the app. You can find the app in the Windows Phone Store