Dictation falls short of Siri integration, but now with Mountain Lion you can now dictate your text directly to your apps.
You first need to enable Dictation Mountain Lion by navigating to: System Preferences > Dictation & Speech > Dictation.
If it’s not enabled and you press the shortcut (Fn key twice) it will then ask you if you want to enable it.
Dictation is available on all apps that you would normally type with using your keyboard, including Safari when filling in forms. You’ll see a microphone on your screen near the insertion point.
Dictation will automatically pause iTunes and stop your Mac fans to create as quiet an environment as it can during recording, and will resume them once you’re finished dictating.
As Mountain Lion processes your spoken words, you’ll see purple dots once it’s ready, those dots will then be replaced by your dictated text.
Your Mac doesn’t convert your speech into text, that’s done by Apple servers, because of that it works only when you have an active Internet connection and you have a time frame of 30 seconds per dictation.
Dictation includes some voice “shortcuts” to allow you to manipulate the text while you are speaking. The following is a list of commands are from Apple’s page on dictation: