At Disneyland our son used his on every ride. Even Space Mountain, didn't on Splash Mountain for obvious reasons : ) , used it on all rides he went on.
Not sure about the concentrators, but I use my m=6's on every ride except for RNC and that is because they do not allow it.
I have never taken my POC to the park for fear that someone would try to take it or it would get damaged from others not paying attention or my losing my grip on it during a ride