a bit skeptical..a LARGE bit
I quote from one of those links in the OP:
"Whenever your wheel tries to move up, the beads counter that movement by moving down momentarily."
I've been thinking about this scheme since I read it here yesterday. With my knowledge of physics, I'd have to say there is NO WAY those beads could react fast enough to compensate for all the 'other' forces on the tire besides just its centrifugal pull at the 'high spot.' Every time one hits a pothole or any substantial bump, the tire will "try to move up" and the beads will be trying to keep up. No way they could keep up with that much continual adjustment. The centrifugal force (plastering them against the outside of the tire space) would NOT allow them to roll freely enough to readjust quickly enough. Let's face it..that heavy spot is only "trying to move up" for half a rotation...mere micro-seconds for each rotation of the tire.
How would one test these things? Anecdotal evidence like bentwings' isn't really scientific enough, but how about this simple test:
Take a wheel/tire known to be out of balance, put in the beads and test it on a dynamic spin balancer. If it would work on the road, shouldn't it show up as a balanced tire on the spin balancer?
I have stated my unscientific skepticism, but I'd be willing to listen to someone that could perform such a test!!