My analytical colleague Guy Creese on a new Google offering
Google's offering this service for free is a huge step forward. Ten years ago, similar testing of different product package designs would have cost tens of thousands of dollars. A company would have had to create paper mockups, convince appropriate test subjects to take time out of their day and turn up for interviews, and then hire interviewers to ask the right questions and collate the answers.
The Web has changed all that. Now, webmasters can craft alternative graphic designs quickly, users can click at home (and often not even know they're taking a test), and analysis engines can collate the results in realtime.