I read about these about 6 months ago. pretty sweet stuff. Only problem is for winter uses, these won't work since snow and ice would get in their extremly fast and would cause horrible vibrations (throws the wheel out of ballance) I already get this from time to time, and I have simple 5 spoke del sol wheels.
Another sweet part about them is since there is no air, there can be hole in the actual contact patch and water would be able to flow right through them, which means elimination of hydroplanning.