The dig on a shafty crawler like the AX10 works by allowing you to disengage the rear drive line from the rear transmission output so that your rear wheels either free wheel and just follow behind which can be helpful when side hilling or you can go full dig and lock the rear wheels up making it easy to make sharper turns or drag the back end down a steep incline, and IMO yes it is worth the money if you plan on competing, or just want the ability to make sharper turns, I just got mine in and I am still learning how to use it, but it has already helped out a lot....