I've used a Vortex for five years or more and will tell you it's a practical addition to your Weber toolbox. I'm sure that the various "Poortex's" that have built by various members here are also very effective. Of the four cooking options on their website, I've only used mine in the "Indirect-Direct" method, mostly for wings.
I don't the physics of it, but from my experience, using the Vortex (or similar) provides a better cook on wings than just using the charcoal baskets.
Just did 36 wings last night and they came out great.
BD