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When workplace computers moved beyond command-line interfaces to the mouse-and-windows-based graphical user interface, that was a major advance in usability. And the command line itself was a big improvement over the punch cards and tape that came before. We're now entering a new era of user interface design, with companies experimenting with everything from touch and voice to gestures and even direct mind control. But which of these new interfaces is appropriate for a corporate environment, and which are simply not ready for prime time? (Watch a slideshow version of this story.)