It was $25 for 'the world's biggest IMAX screen' in Sydney.

I only noticed one added thing, and that was a 2 second shot added to the Forest Battle, with Optimus wrestling with Blackout, before he is knocked down and draws his two swords.

I didn't pick anything added in the final battle, but will see if I notice something missing the next time I see the regular version.

And everything else was the same though. Nothing else appeared to be added in any other part of the movie. I did notice how significantly cropped/zoomed in the movie was on the IMAX screen. In some scenes it was really obvious when half the heads of various robots were cropped off the top of the screen, who are fully visible in the regular version. I don't know why they did this, because with the larger screen making it more difficult to track the fast, blurry movements, zooming in on the shots makes it even more blurry and difficult to see what is happening, especially any close combat scenes. I had people near me commenting that they couldn't see what was happeing (similar problem with TF1, like when BBee and Barricade were fighting), because the fast moving images were just a big blurred mess, made worse by it being zoomed in compared to the regular version.

(The BCC cinema near me charges $15.50 during the day, which is outrageous, but expected once they created a virtual monopoly when they merged with Hoyts and Greater Union a few years back. I don't think I'll be breaking my 12 theatre viewings record with TF1 at that price.)