YES, VIRGINIA, THERE IS AN AIRBORNE SCROTUM: Saw The Polar Express in IMAX 3D this evening. I really don't have much positive to say about the film--it's a narrative mess with utterly unnecessary sequences including a couple of "roller coaster" sequences inserted just for the visual purposes and a musical performance from Steven Tyler. However, the visual, in IMAX 3D, is absolutely spectacular. The images, which seem flat in TV ads or in a normal 35 mm trailer, jump out of the screen (literally), and decrease the "creepy artificial" issue that has oft been remarked on.
The film nails Van Allsburg's illustration style, at least when there aren't people on screen, and the film looks great. However, Zemeckis should have learned in making Who Framed Roger Rabbit? a lesson he hasn't--the screenplay should drive the technology, not vice versa. Here, it seems like they came up with the technology and the look and then tried to stretch Van Allsburg's short and touching story into something far longer. I think the film might have worked better as a short, just telling the heart of the book rather than the ridiculous plot contrivances that have been introduced.
And yes, while I wouldn't have noticed it before reading the review, Santa's sack does look suspiciously like an airborne scrotum.