Digital Foundry, most known for their analysis of a video game’s technical performance, have released a video report for The Witcher 2: Assassins of Kings running on the Xbox One via backwards compatibility.
The video below shows that when running on the Xbox One the game performs better during cutscenes than on last generation’s console. During combat, however, the framerate does drop a little bit compared to the Xbox 360, though nothing substantial. Also of note is that in the opening cutscene some screen tearing will occur no matter your platform. You can read their full report, as well as other backwards compatible games, here.