Well they maxed out the hardware as they said. But when you write code there are ways of writing loops instead of recursion to optimize code. Really unnecessary for small programs, but incredibly important for large ones such as video games. Optimizing code can lead to an increase in performance.
The tricks they speak of are just ways to intelligently run each SPU at 100% and utilizing the gate delays on the hardware to use parallel processing. (While it's waiting to receive a value from memory it can go fetch other values, or move values, etc. Memory is slow.)
Great news though. I can't believe Bungie is speaking with Naughty Dog. Very interesting indeed. If Halo does indeed come to PS3, and is good, I believe more consumers would choose PS3 over Xbox.