@Oshyan - I'm slightly surprised that you found IMAX fuzzy - I didn't notice this - although obviously, if you take the glasses off it looks horribly blurred. I wonder if you had a pair of sub-standard specs?
I also wonder if the 3D effect varies with your position relative to the screen - I went to see it again in a regular theatre, still in 3D, and it seemed that, in places where the 3D was marked in the IMAX theatre (like the landing of the shuttle at the start), it wasn't so obvious, and conversely, I don't remember being "surrounded" by the falling ash after the big destruction scene in the IMAX, but it was very evident in the regular theatre. Does anyone know of any evidence for this?
Edit: Apparently the 3D system in IMAX is different from regular theatres, so that might explain the discrepancies noted in my previous para.