My vest (Afflovest) I thought was helpful but it gave me rib pain so I had to discontinue. From what I've read, percussive vests work best when used regularly, and over time they do help with loosening the mucus from the airways. It's another tool in the toolbox and by no means magic. It works better for some than it does others. If we take a multi-pronged approach to clearing our airways, I think that's when we get the best results.

As @mtyler points out, it's likely these vests were created for the CF community, and used a lot in children, where their lungs are young and pliable.