The ability to function as a virtual assistant, even at the level of a not-so-sharp intern [1], would be a killer app.

Give it some parameters for a trip you're taking. It comes back with some options and follow-up questions. We are a long way from that point. Even that not-so-sharp intern has a huge amount of internalized knowledge about general preferences, cities, airports, etc. and probably knows questions to ask to narrow things down.

I strongly suspect there are other domains where a lot of people are assuming we're 90% there and we're not.

[1] Not to insult interns or any other group. I just mean you don't need to be at experienced executive assistant level to be really useful.

Agreed, determining human intent is really, really, really hard. There are some many context clues we use in everyday life that the voice interface will never have access to like where am I standing, what's my expression, etc.

Makes me wonder if Watson will do a better contextual search and single result answer. IBM should release a voice assistant too.