Depends on the person. I like Pinball, but I'm not knowledgeable about the history or designers of Pinball, so their signature wouldn't mean much to me, other than a novelty.
But if I had a movie themed pin, having it signed by the stars of the movie featured on the backglass would be pretty cool.
But as someone said above, me getting those signatures would be pretty cool and a great feature. Buying the machine with those signatures already there would still be cool, but less so.
Make sense?