If there's one thing Nvidia brings to the table, it's the ability to bring power to mobile platforms.  Just look at the Ion (for Atom-based systems) and the Tegra (for mobile devices like the Zune).  Both bring H.264 hardware acceleration and and the potential for light gaming to traditionally weak mobile platforms.  While I will admit that Microsoft still has some work to do to improve the experience of gaming on the Zune, it has potential to truly bring the Xbox360 a companion mobile gaming device (and mend their relationship with Nvidia along the way).

Check out this video with demos of PGR Ferrari Edition and Vans Sk8.

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