As an amateur who is trying to stop lifting up and changing my spine angle during the backswing, then dipping down during the downswing (resulting in either too steep an angle of attack or hitting irons fat occasionally), I am really trying hard to mimic Dustin Johnson's relative spine angle positions. Man he hits the ball a ton without any apparent effort!
While I appreciate the comments above, I do not understand what is meant by having lag at impact. I thought the proper position at impact was to have a straight line from the left shoulder through the clubhead at and immediately past impact to make sure you are achieving maximum speed through the ball. If he still had lag at impact, wouldn't that mean that he has not yet fully extended his arms and released the clubhead yet?