I am running the PowerBook's GPU at 553.50MHz core and 301.50MHz mem. How much will this little thing overclock to?
Assuming OCing is possible at all, not much. Notebook cooling is often minimal in order to maintain lighter weight and mobility. Mobile GPU's are also intentionally lower clocked due to power constraints as laptops typically run on 45W - 90w power supply, in addition to the thermal constraints from the minimal cooler. Again, this is assuming it's even possible as often you are locked out from OCing on a BIOS level.
Only x86 users use a BIOS to overclock. Real computer users flip DIP switches. Hardware overclocking is where it is at! This is for the GPU, so I just use software. But for CPU, switches are fun.
Well, even if you aren't locked out of the function, it would seriously be hindered by the form-factor. It's not meant for overclocking.