What is Imax 3d like?

So I'm excited to go see Trandformers 3. I originally planned on seeing it in traditional 2d film projection, but then I heard in Imax 3d I will be holding on to the seat during like a scene where someone's falling or a plane is crashing because it feels like you're there. Is it really that intense? How is the 3D and how big is the screen?