"The number of atoms in the entire observable universe is estimated to be within the range of 1078 to 1082."
Thank you Google! http://www.google.com/search?q=how+many+atoms+are+in+the+uni...]
Actually, they all seem to me pretty limited compared to the answers you get from Wolfram Alpha.
Also c.f. the responses to one of their test questions, "how much is a quarter cup of butter?". Google makes fun of the inquiry. Wolfram Alpha gives you a thorough nutritional profile, and links to variations based on international cup sizing and different types of butter.
The result Google also gives you is wrong (since its also a just a snippet).
In the article, the question "How old is the Lincoln Tunnel" struck me as incorrectly formatted for the parser (I know, that's the point), so I asked Siri, "When was the Lincoln Tunnel built." The Wikipedia article on the Lincoln Tunnel was returned. Wolfram Alpha was listed under other sources, so I chose that. The response? "1937"
Luckily if you say "Wolfram XXX" instead of just "XXX" Siri will route your question straight to Alpha no-questions-asked.
It's also worth noting that Siri gives more verbose answers in "Hey Siri" mode, presumably because it assumes you're not looking at the screen.
Just a formatting issue.
Solving it isn't really easy, either. When reading a document is a caret a power, a regular expression operator, an exclusive or, or a nose on a smiley? :^)
A lot of context identification work has to be sorted out for smart agents to succeed.