If you press down the "S" key or Show button, the phantom will start to animate; whenever you let up on the key, it finishes immediately.
So the old behavior is identical: press "S", see the phantom. But you can also hold it down to have it animate.
Additionally, you can now hold down "S" while writing if you really don't want the phantom to fade out. (Several people have asked for this, but it's dangerous because it makes it surprisingly impossible to learn anything if you're tracing it).
Later on, animation speed control will be coming as well.