At last, some data. David Talbot got a login id from Wolfram and ran some comparative tests. For example:

SEARCH TERM: 10 pounds kilograms

WOLFRAM ALPHA: The site informed me that it interpreted my search term as an effort to multiply "10 pounds" by "1 kilogram" and gave me this result: 4.536 kg2 (kilograms squared) or 22.05 lb2 (pounds squared).

GOOGLE: Google gave me links to various metric conversion sites.

Tentative conclusion: the semantic web is still a long way off. The problem of search is only about 5% solved. Google accounts for 3% of that. Mr Talbot’s experiments suggest that Wolfram isn’t going to move it much beyond 6%. Still, it’s progress. And Google could do with some competition,