Navigation: The “next” link is very small and it's in different place on every step. A fixed navigation and/or bigger link would be nice.
Also, showing me that it's “Step 3” is useless to me - I can count myself and even if I couldn't, I don't really care how many steps I've already seen. I'm more interested in how many more there are.
There should also be automatic scrolling so that I could actually see the next highlighted area. If you already do the scrolling, remember to scroll in a way that guarantees to show whole area, not only top line.
Thanks for the great work, I think I might use it in my next projet!