Opt out of Google's new search interface

Question

I think Google is testing a new search interface. I don't like it. How can I get the old Google search interface back? I've heard stories about setting cookies to enable certain unreleased features; can I do the the same to disable this one?

The new search interface replaces the search results sidebar menu with one on top and also increases the results' font size:

I can get the old interface back by browsing in private mode or using a different browser (clearing cookies does not work.):

Answer 1

Google are currently releasing the new layout, so soon there will be no avoiding it. According to their blog:

It’s going out to Google.com users in the U.S. to start, and we want to get it to users in other languages and regions as soon as we can.

So for the moment you could use another region like http://www.google.co.uk but probably not for long. Since others will no doubt dislike it there will probably be some Greasemonkey or similar script to send it back to the old look eventually.