Yesterday Microsoft updated the Windows Phone version of the Xbox Smartglass app. As is often the case with Windows Phone updates from Microsoft the release notes don’t give a clue as to what the update is but I did notice that the little black bars at the top of the app have gone and looking at various sources on Twitter the update seems to have added 720p support to the app. My HTC 8X runs at 720×1280 so it now looks much better.
You can find the app in the Windows Phone store