From the PlanetXbox360.com feature preview:
"First and foremost I'm a PC gamer. So, what am I doing writing about the Xbox 360 edition of The Witcher 2: Assassin's of Kings? I've already beaten the game, twice in fact, so why should I even care?
Well, for one, there's new content. More than four hours worth. There's also been a vast array of improvements made for the 360 edition. Improvements that make even a PC gamer like me intrigued.
In fact, after playing The Witcher 2 on Xbox 360, not only is it certainly the Enhanced Edition, but it may very well be the "Ultimate" edition."