This reminds me of the issue in machine translation where even sophisticated systems cannot understand the importance of a word like "no". So, for example, a phrase like "please press this button" could be translated as "please do not press this button" and it could be automatically rated as a good translation because most of the words are there.

But, on the other hand, I have dictated these paragraphs, (pretty much just adding punctuation and minor edits at the end). I think the most useful feature I've found related to voice is dictation (speech to text). It is almost perfect, at least in English (and I am not a native speaker).