The way you talk about the code only using 30% of the Cell makes it seem like there are tremendous bottlenecking problems with the GPU.
It's not like the early PS2 games only worked its processor at 30% of its maximum rate - they were working the processor at maximum capacity, they were just poorly optimized. Games get better over time not because developers figure out how to use more of the processor - that's easy. They get better because developers figure out how to do more with less usage.
Edit: To clarify, it's absurdly easy to increase processor usage - write more code. Place more enemies, etc. If you're not using the whole capacity it's got to be because non-processing issues prevent you from doing so, such as a video card that can't handle what you want to add. My understanding of all of these "we're only using X%" statements was similar to HappySqurriel's. It's not a measure of processor usage but a measure of processor efficiency, which is probably a flop ratio and which is probably artificially low because of the PS3's absurdly high theoretical maximum.
