Sorry to bring this post out of the mothballs, but the ability to dimension a 3D sketch point to a work plane is new to me.
I've done some experimenting (IV2009), and it doesn't appear possible to dimension a skew line to an origin or work plane (to control the absolute angles from horizontal, vertical, etc). I know Inventor can figure the angle, because the measure angle tool brings up the correct number instantly.
Is there a method to accomplish this that I'm missing, or is this functionality still not available? I know how to accomplish this with 2D Sketches, but I'm testing to see if a 3D sketch alone can control geometry in this manner.