Thanks to Newsarama for the info.
A few years ago, some IMAX theaters would show traditional 35mm films. They would be a bit on the grainy side, but still look pretty cool. But now they've developed a process to re-master the film to take advantage of the unique IMAX setup.
If you're able, I highly recommend seeing a film in the IMAX format. When Attack of the Clones came out, I had to see Yoda jumping and flipping about on a multi-story screen. Was worth it.