What are people's thoughts on multivariate testing?

For the unaware, multivariate testing is a means of improving web performance by testing a number of different variables on a test. It's something marketers love but I wanted to open things up and ask what IT people think about the fast growing discipline?

If any of you are familiar with print or direct mail advertising, it's kind of like a/b/c testing on steriods (ie with the ability to test multiple things at once all in the mix)

Sebastian