There is a new feature in Mountain Lion, Dictation.
When I try to enable it in the System Preferences, I get the following dialog:
In other words, what Dictation does is just record your voice and send it to Apple, which does the conversion of your voice into text server side. This makes very little sense on today's powerful laptop or desktop Macs (I can see why it would make sense on a mobile device though). Is there a way to use the Dictation feature offline?