Just got back from seeing the fixed-aspect 2.35 version, and it works very nicely indeed. The clarity of the IMAX process is still readily apparent, with those scenes featuring a bewitching combination of razor-sharp detail with a smooth, grain-free appearance. And though proper IMAX is wonderful in terms of the expansive impact of the image, the actual composition seems to take a back seat in favour of the sheer scale of it.
Take the bit right at the beginning when the 4x4 is approaching the plane: the shot of Aidan Gillen in front of the aircraft is beautifully framed in 2.35, with the aircraft filling the background of the widescreen image and the actor's upper torso in front of it, but in IMAX you get lots more legs and feet and tarmac. Not every IMAX shot is that bland, natch, but the legs/feet/floor thing is a common throughline. If anything the 1.78 IMAX crop for Blu-ray will help in that regard, because it combines the 'wow' factor of the alternating aspect with tighter framing that goes partway towards maintaining the (IMO) superior 2.35 composition.
luca, mi amico, you're barking up the wrong tree. The filmmakers themselves have sanctioned the 1.78/2.35 version, so if you want to bleat about people not respecting OAR then you'd better hit up Mr Nolan first before chiding the rest of us.