I've never had one of these power balance things, but I do wear a Trion Z bracelet. I'd been having poor society days after poor society day. I'd struggled to even get 30 points for a couple of seasons. So out of desperation I gave this Trion Z bracelet a try for the last event of the year, two rounds of stroke play.
I know it wasn't scientific, but I played really well with the bracelet on, and finished under par and came second. I've worn the bracelet for every round since, and wouldn't be without it. As far as I'm concerned they work.