The difference is about $3 as far as I can tell. We've seen a few 3D movies, and while it was neat the 1st time or 2, other than that it was *meh* Doesn't change the story. If it's a good movie, it will be a good movie either way. If it's a crappy movie, it will still just be a crappy movie in 3D. I don't think it makes or breaks a movie, nor does DH, who is a movie snob.
On the other hand, the 1st one we saw in 3D was My Bloody Valentine, and that was kinda neat, especially when the blood came flying out of the screen and the axes and what not. But we're horror movie geeks as well.
Nan