This is one of the better videos I have found of TC ONLY performance. Its in french but, it translates to without CDL
http://www.youtube.com/watch?v=nc1kzHhtvmM
That is a great video! Look just after the 2 min mark. You will notice the truck gets stuck on a rock going up hill (similar to Justin video). Even though his traction control seems to work very well he can't get over the rock. He has to back up and use some momentum to get over the rock. I would bet that if he could lock his transfer case he wouldn't have had to back up and would have been able to get over the obstacle with lower speed and less wheel spin, which i believe is the point of Justin's video.