Earlier today, Roger Ebert posted a letter from Robert Murch. If you aren't a film geek, Murch is a multiple-Oscar award winning editor. He worked on "Apocalypse Now" and "The English Patient" and is pretty much the best at what he does. Murch doesn't think 3D will ever be a viable mainstream technology.
Most of his argument comes down to the fact that 3D films require our eyes to converge and focus at two different points. This is something we are capable of doing, but not without significant additional strain. Which is why headaches are such a common symptom of extended 3D viewing. Our brains just haven't evolved to handle it.
No one can argue that the convergence / focus issue isn't a problem, but there seems to be considerable argument as to whether or not it is an insurmountable one. CrunchGear weighed in a little earlier, and noted that convergence / focus is merely a limitation of the technology. Basically, film-makers who use 3D without going overboard have a powerful tool in their hands.
[Via Sun Times]