What would be the benefit of this, besides from looking cool?

More accuracy. Like others have said, homonyms (their, they're, there) is easier to determine once you have more context. So then you may need to go back a couple words and update them.

Same with punctuation, you could determine that a comma belonged in a certain place once you have enough words.

In iOS this means you can edit the text as it’s being transcribed. For example, I want to dictate a todo list and after each item I can hit enter to go to the next line.