"My go-to sites for deciding on formats: http://realorfake3d.com/ and http://en.wikipedia.org/wiki/
Of course, I'll have to start noting which theaters have 48fps or laser projection soon. And it isn't easy to tell which cinemas are too lazy to take off 3-d projectors from their equipment for regular blockbusters...."
Basically, if Mission Impossible was filmed partially in IMAX (it was), then it pays to see it in IMAX. But only on an actual IMAX screen. A version of the true IMAX map for google maps (rather than google earth) can be found here (stopped updating about 2010?). The original brouhaha kicked off here.
Then again, I really enjoyed seeing the Watchmen midnight on a (true) IMAX screen, despite the fact that it wasn't shot on IMAX. And considering the problem outlined by the Boston Globe above, IMAX projection is likelier (I think) to be better quality than your corner multiplex. Depending on who is running it.
We should probably all just go to the art house cinemas with flawless projection of older films. Simpler, really.