I have never used AutoCad but I know about the selection method and I find it useful, so i think this doesn;t only concern ex autocad users. This selection method could also work with a hit of a button+shift and mouse to any direction to either select partialy the elements or not..Kliment is right, it could be just a checkbox in the selection methods.
I've raised this one before (see 'Arrow Tool Mode Selection' further down the same page).
Frankly I wouldn't care whether you have the facility to select mode by the direction of the drag, or by a shortcut key. As long as it doesn't take 2 clicks to do it.
As I've said already, what's the point of being able to select the arrow tool with a shortcut, if you then have to take your eye off the ball to select the mode? (Back to dipping your pen in the inkwell by the side of your drawing board!)