Wolfram Alpha will attempt to give you real answers to real questions - not just a list of relevant links. So, if you type in 'how long does it take to fly from New York to London' you will get a real answer such as 7 hours, not just a bunch of relevant links a la Google.
The huge question is is Wolfram Alpha competitor to Google or partner? Given that Google is desperately, behind the scenes, trying to come up with a similarish service - they see them as competitor first. For us users they should be hugely complimentary Wolfram Alpha gives you direct answers to your questions, Google gives you links. But guess who Google's gonna try and buy damned soon??