I have never used it mainly because my curiosity has never been piqued enough to find the time to explore a bit with it.
Have you tried it? What was your experience? I am glad now that I never really tried it out.
From what I gather, hitting that button these days is a one-way ticket to a spam website. There is a security lapse in the coding technique associated with it:
[.....Unlike phishing links, search engine spam can take advantage of special parameters found only in search query URLs. Google, for example, supports the BtnI parameter. This is associated with the "I'm Feeling Lucky" button, which sends the person clicking on the button directly to the Web site associated with the top search result for the given query, without first loading the standard Google search results page.
By using this parameter, a spammer can construct a URL that looks like it points to Google, but will take anyone clicking on it one step further, to the top-ranked site for the query. If a spammer has not managed to manipulate Google to present his or her site as top result for the query, adding the inURL parameter accomplishes the same result. This parameter restricts the search spam query to a single site, which guarantees the top result, the one to which the searcher is automatically and unluckily redirected, is the spammer's malicious site.
"Google works hard to preserve the quality of our index," a Google spokesperson said in an e-mailed statement. "We actively identify sites that serve malware or abuse our quality guidelines in other ways. Sites that exploit browser security holes to install software (such as malware, spyware, viruses, adware, and Trojan horses) are in violation of our quality guidelines and may be removed from Google's index. The same is true for spam. We regularly remove spammers from our index."
Last November, Google removed tens of thousands of malicious Web pages from its index. The company will almost certainly continue to do so periodically for the foreseeable future. It's likely that Google will eventually curb such abuse; other companies like eBay have already taken steps to prevent similar URL redirection tricks.
Sunner of MessageLabs also noted a rapid rise in the number of targeted phishing attacks.....]
