Starting with OS X 10.8 Mountain Lion, your Mac could take dictation. But, just as with the dictation feature on iOS, the OS X incarnation required an Internet connection, couldn't show its progress while you spoke, and could only listen for about 30 seconds at a time.

That all changes with a single checkbox in Mavericks (OS X 10.9). Fire up System Preferences and click on the Dictation & Speech pane. There, you'll find a checkbox for Use Enhanced Dictation. The first time you check it, you'll need to wait out a hefty download (between 700 and 800 megabytes), but once you're done, you can dictate a lot more freely.

Now, transcription happens on your Mac, not Apple's servers. And you can see the transcription appear as you speak, in real-time. In fact, the cursor remains active too; if you see a mistake, you can click around (without speaking) to make your edits, put the cursor back where it needs to be, and start talking again. Unfortunately, however, Mavericks doesn't offer any ability to use speech-based editing tricks: If you say "delete that," Mavericks types "delete that."