The spline tool is actually more functional than their patch notes seem to suggest. I am playing around in the spline content examples and it is pretty sweet. They have lanterns swinging on a spline as if in the wind, a particle effect that follows a spline in a pattern, a plant that grows from almost nothing into a 6 foot long vine, and then they have a fish that you can swim and jump around the room and its body moves all fish like using splines.
From looking at the blueprints for those examples, I would have to say that you can make splines do just about anything you could think up for them. Still trying to wrap my head around the math and what each spline setting does.