I would love to see a way to make more precisely rounded shapes with the otherwise-pretty-great pen tool in AE--like the curvature tool in Illustrator does. Perhaps the entire tool doesn't need to come in--for instance, if you had a rectangle, you could insert a point on two sides would define the ends of those edges' straight points (defining the beginning and ending points of the curve), delete the existing corner vertex, select the two newly created define-the-ends-of-the-curve points, right click and choose "create curvature", something like that. There would be no need to have any options--the curve itself would be defined by the locations/angles of the defining/connecting edges.