These extensions, up to 25 characters, look an interesting addition, although, it's adding more clutter, imho.
Whether it’s free shipping on all laptops or a price match guarantee on smartphones, the more information people have, the better purchase decisions they can make online. That’s why we’re introducing callout extensions: additional text that shows with your Google search ads, highlighting specific information about your products and services. Callouts will start rolling out today, with full availability to all advertisers in the next few weeks.Google AdWords Rolls Out Callout Extensions Allowing Additional Text In Search Ads [adwords.blogspot.com]