Here's a screenshot:
According to Google, "If your online store is rated in Google Product Search, you have 4 or more stars, and you have at least 30 reviews, you'll automatically get seller ratings with your ads. What's more, you'll only be charged if someone clicks on the headline of your ad - clicks on the review link are free."
No official announcement from Google about a roll-out to additional countries yet. According to this page, ad campaigns must be targeted to the U.S. to appear with seller ratings extensions.
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!