The most strident objectors to the kipping pull-up advocated by CrossFit have been the kettlebell swingers. They despise our "sloppy" pullups. Other communities have been confused by kipping but are ultimately receptive to it after an explanation of our reasons. The reaction of the Kettlebell community has been to call us a cult.
I know how much they love swinging kettlebells, so here is my attempt to show that their flavor of Kool-Aid is really not that different from ours. The trajectories of the kettlebell swing, snatch, and clean are eerily similar to the trajectory of a kipping pull-up. Both use horizontal displacement to generate momentum along an arc that ultimately produces vertical displacement. In simpler terms, the backswing adds power to the movement. My grandpa had a good term for this motor recruitment pattern. He called it "the old heaveho."
Dragon Door's brochure claims, "Amazingly, the Russian kettlebell will make you good at many things you have not practiced. Gireviks report on our Strength Forum that they run faster, bend sixty-penny nails, bench or deadlift heavier, etc., just from lifting kettlebells. The only time they see the barbell, a nail, or running shoes is during the test!"
I put emphasis on the heavier deadlifts because it goes to show that the ballistic loading of kettlebell swings can improve your limit strength. If you look at Dragon Door's testimonial page, you will find no less than eight happy customers who report new personal records on the deadlift following a period of nothing but kettlebell work.