I can tell you what's so impressive: 1.) It does not just answer isolated questions but it has a reprentation of the discourse. You see that when guy in the video follows up on a previous query related to mortgages. 2.) It is incremental, that means it starts processing the input while you are still talking. That's what allows it to be so fast. In principle, that allows it also to interrupt your sentence and ask for clarification. 3.) It has good understanding of complex topics and that allows it to ask clarification questions and additional details needed to answer a question.