Were the Pyramids made of cast concrete blocks?

A recent story in the Times Online (UK) discusses a theory getting serious examination: The higher-level blocks in the pyramids at Giza were not hauled to the top, but cast in place out of a lime slurry made from lime dug up very near by. Limestone concrete, well before the Romans became the concrete masters of the ancient world.

If the theory is confirmed it gives a very impressive picture of the expertise of ancient Egyptian engineers. I have had the usual view, well represented in the scholarly literature, that the Egyptians did things the simpler, even brute-force way, such as using repeated subtraction instead of inventing division like the Mesopotamians did. My view may need some revision.