The searcher first sees a few results for specifically what they've entered. Then, the searcher is asked if they're "dissatisfied" with what the results they're seeing. Without needing to click, a suggestion is made and a new result(s) is listed. I'm thinking of it of variation on a traditional spellcheck.
Btw, I tried transposing letters of acronyms and also misspelling words and was unable to find a "dissatisfied" option but I rarely seem to be able to see Google UI test on my home computer.
Postscript: Google has confirmed this UI test.
Meet Your Favorite Search Engine Watch Contributors
Many of SEW's leading expert contributors will be at ClickZ Live, the new online and digital marketing event kicking off in New York (March 31-April 3). Hear from the likes of: Thom Craver, Josh Braaten, Lisa Barone, Simon Heseltine, Josh McCoy, Lisa Raehsler, Greg Jarboe, Dan Cristo, Joseph Kerschbaum, John Gagnon, Eric Enge and more!