Well, you can make an item in Personal Menu that does this (make sure you "Run as root"), or you can gain root, make a text file like /sbin/cpu-perform and put the code in, then do "chmod +x /sbin/cpu-perform" to make it executable. Then you can just gain root and run cpu-perform to get the speed boost.

This only sticks until reboot.

As for "pegging" the processor, it seems that the "on demand" mode that our processor is normally in doesn't really use the full speed of the processor very much (if at all -- my processor never shows more than 330 mHz), even when you're running an app (like OOo) that really pushes the CPU hard. The performance mode seems to let the processor "out of the cage" so that it can run at full speed.

(Alternately, you can install liqbase or the next version of my Easy Debian.)

EDIT: Further testing seems to indicate that the processor does spike up to full speed in On-Demand mode, but I guess that lag between "I need the processor" and "here you go" makes for a slower experience.