...only needs to watch the demo on the front page of MacRumors.
or go here:
http://www.youtube.com/watch?v=L4D4kRbEdJw&feature=player_embedded
Siri is a gimmick and irrelevant. Using your hands is still more accurate than speaking, and there are few circunstances in which using your hands isn't as viable as talking (in fact, I can think of many circunstances in which using hands is more viable than talking).
Funny fact: I'm in Brazil. The iPhones released here are translated to Portuguese and adapted to our country (phone number syntax is different from what the Americans use, for example). However, the spell check system is horrible; when I'm typing in English or in Portuguese, the automatic correction keeps suggesting words that don't exist in either language. And that's with pure text, which is easy to fix. Imagine how poorly the voice recognisition system of Siri is going to work here.
The lack of a big update is underwhelming; I was expecting more than just a slightly faster iPhone 4 with a slightly better camera and a gimmick feature. What I'm really disappointed with is that Apple has kept the "glass brick" design, instead of picking something actually ergonomic.
This may be a shock to some of you, but I'll just keep my current 3GS (if it breaks, replacing it will be cheap, at least). I hope the next iPhone (5? 6? 4GS?) will actually be revolutionary, instead of just slightly evolutionary.