At $25 a pop, I think I'll still be buying spacers. GearClamp doesn't seem to have any advantage: looks no better than spacers, weights about the same (or more?), and introduces an impossible to measure, tiny-miny aerodynamic drag.
Ghetto is right. Though it probably works well enough, it has kind of a jerry-built aesthetic. I'm not much of a weight weenie so a few grams isn't going to matter to me. But looking at a cog that is visually clamped to the naked spline wouldn't instill me with confidence. Plus it seems like the spline would fill with dirt and gunk and generally look like crap. Probably why that website was light on images.
Still, another option for conversion is a good thing. Especially if your not an aesthetics Prima donna like moi.