Here is what Walter Murch wrote to Roger Ebert regarding 3d.
While a large portion of both the media creation and consumption industries gear up to produce and support 3D films and video, others are digging in their heels and asking about the fit and fabric of the emperor’s clothes. Much loved sound designer and film editor Walter Murch – as well as film curmudgeon critic Roger Ebert – are two of those questioners. This blog post by Ebert reprints a detailed letter from Murch about the inherent technical issues of stereoscopic films that detract from the esthetic appreciation of them as well. It’s quite meaty – I suggest you go read it all – but the central issue Murch brings up is what he refers to as the ‘convergence/focus’ issue: “3D films require us to focus at one distance and converge at another. And 600 million years of evolution has never presented this problem before.”