Will it help you dunk, no
Will it help you run faster, no
Will it help you do anything better, probably not.
What is it good for? To prevent old guys like me from hurtin' :)
I run, (or used to) and whenever I got to mile 8, my left knee would start to hurt. Once I put it on, I stopped feeling that pain. So for runners, it's great. Never really felt this pain in basketball as a lot of my friends wear it when playing ball, but from the way they use it, it seems like it works. Just make sure you wash it, it soaks up your sweat.