As I guessed from seeing the IMAX version myself, there was very little extra footage in it, over the regular release. The most obvious was the Forest Battle Scene (which I noticed), but the other area of added footage was in the Desert Battle, which was so minor, it was no wonder I didn't even notice it.

But I think the point of the IMAX version was having certain scenes (that were in the regular version) filmed in IMAX as well, rather than a whole heap of new footage like we got with TF1's IMAX version.

http://www.seibertron.com/transforme...footage/17319/

That link has list of about a dozen distinct differences between the two versions, written up by some people who played both BluRay versions side-by-side to spot even the slightest addition of something.