You are correct, writing code for a CPU is a breeze on the Xbox360, it is actually easier than writing on the computer. This is because they already had an established system to work with. They already had the early technology of the parallel processing, but did not have any easy interfacing with it. That is what DX11 Compute will take care of. If Sony had waited for OpenCL (which is like DX11 Compute) to be published, they could have had a significantly easier game development process. As I mentioned in an earlier post, it was just too early for them to release the hardware. There was just not enough support for this kind of processor at the time.
The architecture behind all 3D games is HEAVILY matrix and quaternion oriented. This makes parallel processing a must. The speed of these calculations are what makes a game run well, or run terribly. Just think of this, for every frame, just for your one character on screen to animate with no special graphical effects (ie. no light, no texture, etc), thousands of computations are done.
From a professional stand point, dedicated parallel processing units is not a speculation, or an obvious next step. It is the next step. Oh, video game development is my job
