"Last January we introduced a video website especially for people who wanted to access YouTube videos through their Sony PS3 and Nintendo Wii game consoles. You could say we've now "expanded" on that. Just as there's a YouTube browser for mobile devices, the new YouTube XL is optimized for watching YouTube videos on any large screen," mentions the YouTube blog.
The XL interface is less cluttered, easier to use, but it lacks some of the features that are available in the standard version of YouTube: rating videos, posting comments.
In other related news, YouTube's player no longer displays the navigation controls in the full-screen mode when you don't move your mouse.