CNET spends quality time with the iPhone 4S' Siri voice assistant to see what she's all about.
Siri: Smart, sly, and sarcastic
Siri quickly has emerged as the most talked-about feature on the iPhone 4S. Part personal assistant, part encyclopedia, and part friend, Siri follows your commands and attempts to deliver information when you need it. I spent quality time with Siri during my second day with Sprint's iPhone 4S and asked her a long list of questions. I tried to stump her, and I succeeded at times, but she also surprised me with the range of factoids that she keeps stored away. And like I said, she's got an attitude.
When I first used Siri the day the iPhone 4 was announced, she wasn't able to come up with the capital of Canada. Since she interfaces with Wikipedia, I was surprised not to get an answer, but she did reply correctly when I used another iPhone 4S just over a week later. So, good for her.
When you ask for distances to a city in the United States, Suri answers with not only the mileage but also directions in Google Maps. At this time, however, she is unable to offer mileage to cities outside the U.S. If you ask for the distance to a Canadian city, she'll offer to do a Web search. But when you ask for cities overseas (like Tokyo, for instance) she'll say that she's unable to answer.