I use them and have been for the last 3 years. When I wear out the tire, I drill a 2" hole in the tire, dump out the beads and re-use them. Great stuff as far as I'm concerned - lets me avoid the local stealer for one more thing.
August of 2015, I had my rear tire replaced. The counter guy was hawking these beads, promised to make it right if they didn’t work as advertised.
They work, no funny ware on the tire, 10 months later 3,562 miles later, I can not tell any difference from day one.
How do they work? It is F/M to me. Freak'n Magic.