I noticed when I saw 'Avatar' at the Metreon IMAX a few weeks ago that if I tilted my head even a little sideways the 3D effect broke up. Unlike in the old days when the lenses in the 3-D glasses were one red, one blue, neither was colored this time.
I wonder if the 3D effect doesn't have more to do with polarization than with color separation. I assume one lens is polarized horizontally and the other vertically. Which would make one of the two images on the screen visible from the left eye and invisible to the right eye, and vice-versa for the other lens.
If the two images were separated more for foreground objects and less for background objects, it would produce the appearance of the foreground objects being closer and the background objects further away. Which is just what one sees.