It's looking like dual graphics will be the default scenario pretty soon anyway. Not in the sense of two graphics cards as in SLI or Crossfire. But more like a combination of graphics cards and integrated graphics. Both Intel and AMD are working towards their combined CPU/GPU chips (Fusion, etc.). So in the not too distant future I can see all machines having a default integrated GPU built-in. Then high-end gamers will invariably add-in a high-end GPU. So why not make use of both resources? Instead of using either the integrated graphics or the add-in graphics, use both at the same time. It doesn't have to be for graphics alone, but it could also be used for OpenCL and DirectX 11's physics engine.

Well we'll see. Even in a two chip package, Silverthorne, depending on the power management and idling features, might net out a better total watts/hour of use. Remember that it will accomplish most tasks much more quickly than a geode will and will probably be able to get back into sleep/idle sooner.

Better Watt/hours? What do you expect they're going to be doing with these laptops, running Folding@Home simulations? The XO laptop comes with a single integrated operating system applications suite which is specially designed for this laptop. They're not going to be able to install applications into this thing, nor will they be able to change the OS.
As it happens, the OS is based on Linux, therefore Microsoft is against it, even though the OS is not really a full Linux, just a stripped-down kernel for running the customized interface. The processor happens to be AMD-based, therefore Intel is against it, even though it's not one of their consumer processors, it's one of their embedded controller processors. Both Intel and Microsoft really have nothing to be threatened by it, but neither of them can stand to have a party in which neither of them are invited, no matter how small the party.