Address and impact have two very different looks to them as well they should. However, the angle of the clubshaft is one thing that golfers should try to make look the same at impact as it was at address. A great way to tell if you are accomplishing this goal is to look at your divots.
One characteristic you should observe is the width of your divots. Which should be the same width of your clubhead and should be square or rectangular in shape. The end of the divot can have a slight curve as well. Divots should have a uniform depth front to back and left to right. If your divots look like this you are more than likely returning the shaft to a proper position at impact.
Look at the two photos below Tiger on the left and Sergio Garcia on the right. Two excellent ball strikers who have led the tour in greens in regulation. Notice the green line, which indicates the position of the shaft at address, and the red line, which indicates the position of the shaft at impact, both lines are almost identical for both players. It's no coincidence that these guys hit a lot of greens in regulation. If you study your divots and the toe side of the divot is deeper then the other or you make a narrow divot that comes to a point, than you either have a lie angle problem or the shaft is in an improper impact position.
One cause for these divots is not returning the shaft to a proper poistion at impact or making a "handle high swing"; in which case the handle of the golf club is significantly higher at impact then it was at address. This can lead to shots that travel low since the ball hits low on the clubface. And if the toe digs a little the face will open causing the ball to fly to the right. Shanks are also a result of a handle high swing. What can you do to improve your shaft angle at impact?
The first drill is to simply try to make the handle of the club lower at impact to make your divots look better. Another drill is to make practice swings on a sidehill lie where the ball is above your feet. A final swing thought would be to prevent to toe of the club from touching the ground at impact. Remember this is just a thought and should not actually happen.