When Siri was first available, there were almost no underpinnings on it would be the next big thing or how important it would be. Suddenly, after this general release on a limited hardware, we suddenly find it the next big thing.
When it was first released, a lot of people said that it was the next best thing. Take a look at Robert Scoble's initial coverage. The only problem was that, since it was an app, I don't think they got the level of attention that they were due. If you used it back then, it really did feel magical.
Now that Apple acquired them, they can use their platform to really promote it and get it on everyone's device by default, which will help a lot more people to find and use it.
I guess most of us here in hacker news would have known Siri (from Sri) from its first public release. Many of us here also would have watched that Youtube video describing this amazing combination of technology. I guess I didn't feel any magic comes from the fact that I am not living in the US (so the app means nothing to me)
It's because it's integrated with more things in a more useful and immediate way, taking it over the threshold of (just) being a geektoy and into being something useful. In standalone app form it wasn't considerably faster/easier/"lighter"/more useful to use for much of anything. Now, some of the most tedious tasks one uses (or would consider using, if the tasks were less tedious) a phone for aren't tedious anymore.
Makes sense to me. Most people aren't seeking out software that is a radical departure to what they're used to. They are only interested when it becomes popular. Apple does a great job popularizing technologies and bringing them to the masses.