This paper focuses on two commonly-made claims about the utility of speech input: (1) It is faster than typed input; and (2) it also increases user productivity by providing an additional response channel. These claims are investigated, both through a review of research, and through an empirical evaluation of speech input. The research review supports both claims. Further, it suggests that speech input will be more beneficial when users are engaged in multiple tasks mapped onto multiple user-response modalities, and when speech is used in tasks characterized by short transactions of a highly interactive nature. The empirical study evaluated the utility of speech input in the context of a VLSI chip design package, and compared speech to typed, full-word input, single keypresses, and mouse clicks. Results supported the benefits of speech input over typed, full-word commands, and to a lesser extent, single keypresses. For the restricted set of commands that could be accomplished with mouse clicks, speech input and mouse clicks were equally efficient. These results are interpreted in terms of a general “ease vs expressiveness” guideline for assigning modalities to tasks in a user interface.