Re: @ Keith T
The difference is that Google is an index of web pages; it does not provide knowledge nor gauges the accuracy of it's results--and as a matter of fact, contains no content at all, just links to other resources. You ask it a question, and it will retrieve a list of resources that it thinks are relevant, based on various factors which may even include popularity. However, it only knows what's on the Internet, which as has been pointed out before, even by El Reg's Mr. Orlowski, the Internet is far from representative of the collection of human culture and knowledge.
Wolfram|Alpha is a collection of facts compiled from various resources (available to you for reference), most definitely *not* web pages. It is not an index of, nor it represents a "new way to interact with the Internet"; it is a searchable database with a computational engine and expert system that allows you to combine and correlate any of its myriad data points.
As the article said, the the data sets are currently few, so it is understandable that it cannot respond to every query. However, it should be understood that even this is no small feat, as the data sets contained are vast themselves. Don't think works of Shakespear, think the English language; don't think recent hurricane patterns, think historical weather data for the last century. Surely you can see the potential of such a system if its database continues to grow.
In more popular term, I would say that Google is closer to The Hitchhiker's Guide to the Galaxy, while Wolfram|Alpha represents The Encyclopaedia Galactica.
I suggest you and others watch the demo presentation, where Mr. Wolfram explains and shows the capabilities of the system.