I got started collecting those charms at a shop in AK two years ago while I was waiting for my husband to buy a hat.. I hadn't ever seen or heard of such a thing till that day two years ago. Now I have three bracelets and a necklace.
WDW has an exclusive agreement with Chamilla (or vice versa) and although I started with Chamilla, I have Pandora too. I can tell you that the hole for the Chamilla charms can be too small for Pandora bracelets. My necklace is Pandora and there are a few Chamilla charms I'd like to wear on it and they simply won't thread because of the smaller hole. But others will fit, althought it's tight.
Hope this helps!