set cpu allows you to set the speed of the cpu. if you have 2.2 rooted then you can overclock it. if you have 2.2.1 then you cant overclock, but it is still useful to help save batt. life. i have 2.2.1 and use set cpu setting the mim to 122 mhz and the max at 600 mhz in "scaling on demand" i have noticed that the phone does run a little bit faster, and i have about 60% of the batt left at the end of the day. where as before i was at 40 or less. hope this helps