One of the holy grails of computer science and medicine has been accurate speech recognition. This seems to be a technology that is always 5 years away. Anandtech has a review of Dragon Naturally Speaking and the built-in speech recognition for Microsoft Office 2003. The short version of Anandtech’s review: Dragon is better than Microsoft but both have accuracy issues. There is also the Free and Open Source Sphinx speech recognition engine not reviewed in the Anandtech article.
The accuracy issues pointed out in the Anandtech article appear to be the same issues that have plagued this technology for years. 95-99% accuracy appears good until you realize that this means 5-1 mistakes per 100 words.