1. A method for speech recognition implemented as a plurality of computer processes functioning in a computer processor, the method comprising: converting an analog signal corresponding to speech input received at a microphone into a digital signal corresponding to the received speech input; in one or more computer processes: using an initial recognizer to perform an initial speech recognition pass on a portion of the digital signal corresponding to an input speech utterance of the speech input to determine: i. an initial recognition result corresponding to the input speech utterance, and ii. a reliability measure reflecting a per word reliability of the initial recognition result; subsequent to completion of the initial speech recognition pass, for portions of the initial recognition result where the reliability measure is low, using a re-evaluation recognizer to perform a re-evaluation recognition pass on the corresponding portions of the input speech utterance to determine a re-evaluation recognition result corresponding to the re-evaluated portions of the input speech utterance, wherein the initial recognizer and the re-evaluation recognizer are complementary so as to make different recognition errors; and determining a final recognition result based on the re-evaluation recognition result if any, and otherwise based on the initial recognition result.