My instructor likes to use the jab hand as the feeler hand so to speak. It's obviously a good gauge for distance control that helps guide you in and out of the pocket. One thing though I've noticed is he keeps it still most of the time rather then throw numerous jabs. When I spar I've been doing single jabs here and there, am going with the flow of the group for now. However, when I think about it, the importance of the jab is huge IMO. I don't think he feels that way. If I were to really throw the jab hard and often, I think it could be effective. I may try this next time. I think the jab is underutilized. Look at some of the best boxers like Larry Holmes. That jab would wear anyone down.