Beside's naturally speaking the other product that I've seen references to is IBM's ViaVoiceQuote from Toonces:
Is there a software package out there that's better than Dragon NaturallySpeaking? Someone mentioned a product by AT&T, but I'm unable to find anything on the web.
Quote from Imagine:
i have been studying this industry and the following is the latest comparison data i could find for text to voice
http://www.asrnews.com/accuracyt.htm
good luck and let us know which way you went