best thing to do is to clean everything yourself. Run defrag, check hdd. Uninstall unnecessary things, trim down processes and services in task manager.
all it does is removes a few services from memory while the games are running. so in that respect if your running short on ram it might help as your system wont need to use pagefile as often.
but.
some anti cheat measures see it as a hack so its not a good idea to use it with online games that use punkbuster or similar anti cheat tech.
i know an early version of game optomizer allowed you to manually adjust your fps to help smooth out gamplay but some guys abused it in that they would macro the feature so they could hit a key and instantly drop the fps down to 5-10 fps which causes the game to hitch long enough for them to turn and shoot before you even know its happened. (thus the anti cheat measure)
Like the guys said, it doesn't really help much. It frees up memory if you've got too many applications running in the background. I've used it before, and it never really made any difference on my FPS.