Before Parallax: I scroll down, viewport scrolls down.

After Parallax: I scroll down, text, images, and backgrounds fly all over the place for no good reason. Designer prances around me proclaiming "isn't it so unique!".

When done right (keeping it simple) It can make your site stand out and provide an interesting storytelling experience. Most of the time parallax just over-complicates a simple scrolling action. It's a solution to a problem no one has.

REALLY BAD Parallax: http://journey.lifeofpimovie.com/#!/

BAD Parallax: http://www.nouvelleoctavia.fr/

GOOD Parallax: http://hotdot.pro/en/#

So very good job on the library, the scrolling is responsive and not glitchy and I like the progress bar at the bottom. let's just hope people use it correctly and don't over do it.