Just got back from IM3. Good flick - not the best of the three, though.
The UltraAVX widescreen looked amazing in 3D - and the soundsystem was killer.
But was disappointed with the theatre seats - not what they advertised. They were barely an upgrade from regular theatre seats...all they did was recline slightly - with no way of locking them in a recline position.
I wouldn't pay the extra premium cost next time for the AVX experience.