Both of my parents and myself bought a set for all of us. We also attended the Tuesday night showing of Fantasmic, which was also the premier. Disney gave hats to the dinner package section for free (which caused a LOT of drama), but a majority of the crowd had them as well (I'm assuming they purchased them, but you never know). I admit, it is kind of weird to know they're working but not be able to see them. And I was very grateful that I'd seen the show before, because I spent a good portion of it watching the crowd and the effects instead.
That being said, I do think I'll take them back with me in December for the Osborn lights, which they are supposed to sync with as well. However, I do think I'll most likely hold them so that I'm able to see the lights. If I go to Fantasmic, I'll most likely wear them just because I'll know what they're doing.