Hi, Michael,
I have tried using moi's construction lines. They just don't seem to work well for some tasks. especially in the 3d view (which is the view i like to ideally work in 80% of the time).
I can't seem to draw say a rectangle that is 24 inches tall exclusively in perspective view as easily as i can in application X using its inferencing mechanism. I'll make a quick video this weekend showing what i mean. It is difficult to explain without images.
However i may be missing something or not using the construction lines in moi properly. I have never been able to draw constuction lines freely in 3d view; they always seem to be constrained to the xy plane no matter how much i tumble the view before drawing.

-isaac