I gave dynabeads a somewhat scientific test on my Z....with regular stick on lead weights, it was smooth all the way to 150+. While I was washing it, the weights on the rear fell off. Now there was a faint, but noticeable "hop" once you got it much over 90 that got worse with more speed. Pretty obviously a out of balance wheel. (It was 2x 1/4oz weights that fell off)
I got some dynabeads, the 2oz baggie recommended for the 190 rear tire it has. Added the beads, went for a ride. Tire was aired up to the same pressure as before. No difference. Still had the speed hop. I added the lead weights back on with krazy glue(there was a visible outline where they had been). Hop went away, perfectly smooth again, though now it might have been a tiny bit better than the pre-beads. Tough to tell for sure.
With the rear wheel on a stand rotating it by hand, I can hear the beads freely flowing around inside the tire, so they weren't clogged up by bead sealant or moisture.
These seem to be really hit and miss.