Google Pay Per Action Beta which was launched on March 20 received a lot of unpleasant feedback and the service was available only to a few areas.
However, newly re-unveiled is "A New Way to Pay – Google Expands Pay-Per-Action for Google AdWords". "Advertisers in the beta will see an alert in their AdWords account informing them that they can now create pay-per-action campaigns. Going forward, advertisers who have enabled AdWords conversion tracking and received more than 500 conversions from their CPC and CPM-based campaigns in the past 30 days will be automatically added to the beta on a rolling basis.
Publishers in the Google content network who want greater control over the ads shown on their sites may select between individual ads, a shopping cart of ads, or a specific keyword that is relevant to their site's content. These publisher-selected ad units contain only pay-per-action ads, and therefore, they do not compete in the auction against CPC or CPM-based ads, which are served in separate AdSense for content ad units."
More information available in the press release .