The official adsense blog has announced the avilability of AdSense with Rounded Corners.
AdSense blog --"Recently introduced new formats for AdSense ads. This week, we've added a new dimension for publishers in customizing these ad formats. You've long been able to customize the size and colors of your ad units; now, you can also customize the shape by selecting between square, slightly rounded, or very rounded corners."
To get started with these new ad shapes, visit the 'AdSense Setup' tab in your account. As with all format options like sizes and colors, different corner styles will perform better for different publishers. We recommend that you choose the corner style that best matches the look and feel of your sites. Please keep in mind that if your page background color, ad background color, and ad border color are all the same, these new corners won't be visible.
This new option is part of our ongoing effort to improve the look and feel of our ads. We're also working to give you even more choices to customize your ad formats while maximizing revenue and user satisfaction. We hope you enjoy the new corner options, whether you choose to go edgy or bubbly.
Source:→ Google AdSense BlogGoogle, AdSense, AdSense Round Corners, Featred News, AdSense Features