From AppleInsider's "How Intel's battle with NVIDIA over Core i7 impacts Apple":

If Apple is forced to go back to Intel platform chipsets in order to use Intel's latest CPUs, it will end up with two separate GPU architectures to support, just as it had prior to last fall: NVIDIA standalone GPUs in its higher-end Pro models, and Intel integrated graphics on the lower end consumer models. Intel's integrated graphics (where the GPU is integrated into the controller chipset) are significantly behind NVIDIA's in performance and do not support OpenCL.

Our recent Jobsian history of Apple says that Apple left Motorola and IBM's PowerPC architecture in large part because they couldn't deliver the goods reliably and, as was the case with the G5, iirc, created product delays. Now we see that the x86 world has its own issues.

These are the dangers of sourcing components from different mfgrs, I suppose. Too many competitive chefs in the kitchen, it would appear. I wonder how much grease it'll take to get the palms moving on this one.