Another suggestion.

I find drawing arcs using 3 points to be somewhat unintuitive.

Most editors, you draw the first point, the last point, and then pick the point on the arc, and the circle is calculated through all 3. This way I can get feedback as to what curvature I want.

As it is, I have a hard time using the 3 point arc, if I select start, point-on-arc, end and have it come out correctly. I don't know it's gonna curve until I click the last point, and then it is too late.

Also, it would be nice if "Draw arc, Center" could also be used to draw quarter ellipses. This should be a fairly simple change of a check box, and allowing the arc to pass through the 3rd point drawn, instead of forcing it to stay to a circle.