Whilst performing very well in the desktop market, nVidia has had less luck in the mobile GPU market. ATI has offered stiff competition in this arena, and has held the majority of that market for some time now. nVidia, of course, has plans to change this.
The new GeForce Go 6800 is their secret weapon in this battle. It brings to the mobile world the full power of NV40, in addition to many other new features. But will it be enough to topple ATI from the market, who have scored victories in many areas (such as thermal and power constraints issues) that nVidia have yet to properly solve.