Search engines have long advertised themselves as providing answers, when what they were really doing was providing direction. For example, Ask Jeeves, the first search engine I ever used, originally masqueraded as an e-butler providing answers to your questions, when all it was doing was using your key words to funnel you toward articles it considered relevant.
But Wolfram Alpha really does provide answers. No URLs come back in the results, only a page of often dizzyingly detailed and up-to-date information, like a research report culled by mad scientists with complete access to a universal library. For a telling example, let's compare search results on Google, Wikipedia and Wolfram Alpha for the search term "Pluto."
You can find the results of his experiment here.
Wolfram Alpha really does seem to represent something new, even revolutionary. Clearly, it's not perfect, but if it can improve itself at an exponentially increasing rate, it soon may be close.
UPDATE:> Another brief review here.