The Bezier easing demo is now online. It only illustrates ease-out for a few ease types, but it should be enough to get the idea across.  The following screenshot illustrates the difference between natural and arc-length parameterization for a cubic Bezier curve with cubic ease-out.

Cubic ease-out for two Bezier curves with different parameterization.

The red marker illustrates application of the ease without arc-length parameterization.  The green marker illustrates proper easing with arc-length parameterization.  Although motion along the top curve appears to be eased, the motion is incorrect.  Worse, the actual velocity along the curve is a function of geometric constraints.

The online demo may be viewed here.  The page includes a link to download Singularity.  The demos folder includes the MXML file for this demo which can be modified to test different easing methods as well as ease-in.