My impression is that it's pretty good at parsing words if the input is of high quality and not spoken too quickly. But it's not good at all when it comes to punctuation. It seems that STT doesn't actually understand the concept of English diction and grammar, but rather it tries to transcribe each syllable separately and then glue them together in the hopes that it's a word. Also, the final result is all one long unending stream of text with no punctuation whatsoever. Not great.