“Wii U seems to be a lot more powerful than the previous generation,”  “It sort of fits better into the scalability in terms of graphics performance and CPU performance, so I think it’ll be a lot easier for us to fit it into our scalability model.”

-Gabe Newell

If Valve releases something on the Wii U, it will be the first time the developer has released something on a Nintendo system. Newell went on to say that the Wii U seems to be more powerful than 360/Ps3.

Link