I was introduced to the "left hand roll-under" movement when a comment was made in another thread (on my free, online review website).

I actually now think that it is a good idea that may help a beginner golfer prevent left wrist rollover during the takeaway, and I have therefore commented on it in question number 10 in the backswing section of my review.

See - http://perfectgolfswingreview.net/backswing.htm - if you are interested in my opinions.

Jeff.