The elements and everything used during the scroll checks is in fact cached (which you'll be able to verify by looking at those internals you mention) and throt

The elements and everything used during the scroll checks is in fact cached (which you'll be able to verify by looking at those internals you mention) and throttled per my comment below. As another commenter pointed out, the project page itself is full of drop shadows, text shadows, and css3 gradients, and opacity. Those are probably slowing you down way more than the plugin. Do you see the same performance problem from the relatively unstyled examples?