The problem is clearly knowing where to look. If you try and look anywhere but where the focus point is, it's uncomfortable. The first time I watch something in 3D, it took me a while to learn not to look in the background at anything, to learn to let my eyes be led. Even then, if there is a lot going on, it's not always clear where you should be looking. A mate of mine, a 3D fan, has just gone crazy and bought a massive, high end 3D TV, and even he admits he can't watch it in 3D all the time as it gives him headaches. BR>
3D will only work perfectly when each eye is presented with an image for where it is looking. I'm not being a luddite, if I was still doing 3D modelling on the computer, I think this could be very useful, but I'm not going to buy into this technology for every film. Films are long and the current 3D technology is too much work to watch. Doing proper 3D, with a proper image for each eye (i.e. hologram) isn't happening any time soon.