Ok, I think I got how the slider works exactly and maybe there's no problem with your code but then how come I can't code the simple behavior I want to;
I just would like to launch my effect when moving on a 5%-step slider :
When I move and release the mouse button, the onChange function does fine.
But when I just click on a distant part of the slider, only the onSlide function can do it but it will also launch every pixel I move the slider, so I don't see how one can handle an effect on click somewhere on the slider.
Now I'm pretty sure, that's not a problem with the slider class but I still need to be sure and by the way I didn't find any forum to post this ;p