I've seen a handful of IMAX movies in the science museum. I mean made-for-IMAX films, usually nature subjects like Everest and so on.
I've see just one regular movie shown on an IMAX screen: "Night at the Museum." It was terrible. First of all, the movie was terrible, so I would have hated it on any screen. But second, it was hard to watch on IMAX. My eyes kept jumping around the gigantic screen not sure where to land. Unlike a regular movie screen, where you can more or less take in all the action at once, the IMAX screen makes you pick and choose your visual focus, and it may or may not coincide with where the most action is onscreen.