I was sitting at ROTS with people I work with and couldn't help but feel a little embarassment when I let out a laugh when I heard the Wilhelm scream. They were probably wondering what the heck I laughed at.
I can't remember where I first heard about the Wilhelm, but ever since I've been looking for it in the prequels.
I'm glad it happened early, then I could get down to business watching the film and not thinking about it. But, boy, was I happy to hear it.
I agree, though, it shouldn't be overused. I don't want to hear it in every movie. Just Star Wars.
Ahh, my last Star Wars Wilhelm. *sniff*