I think easing it more of an issue.
Say you have a ball bouncing. In animation, when you ease, you try to make the ball accelerate and decelerate. In some animations (lets look at the headbutt animation), the movement of his body is constant. If you think about real life headbutt, you'd move your head back slowly, then make it go very fast towards your opponent. Upon collision, you would bounce off a little, then slow down back to normal position.
Easing can be very difficult, especially with linear animation, but it improves animations vastly.
--donut3.5--