It would be nice if it was possible to only scroll the page either vertically or horizontally. The code should look at the client width/height and the scroll width/height to determine which orientation is scrollable. It could also look at the current scroll offset to determine that it shouldn't scroll anymore once it has reached the edges.

With this in place I think a further improvement would be for it to look for scrollable parents, so that it is also possible to scroll overflowing elements, not just the body.