Screwing around with CPU time cycles for a game, or for that matter, any application is beyond asking for trouble.
I mean, I'm no hardware expert, but the engineers at Intel are. I trust them more than some muppet in a basement hacking hex code to change the behavior of important and relatively expensive hardware.
I too thought of using that until I read more about it. It could very well work without issue for most. Yet, I am not willing to take that risk just for a game IMO.
I take it you don't overclock either?