Google has announced they launched a new AdSense ad unit format and design to spruce things up a bit. Google said the "new format allows for higher performance with a more beautiful and user-friendly appearance."
The new text ads feature elements such as a shaded background and a centered button which bring together the parts of the ad into a cohesive whole. It goes with the "material design" theme that Google is aiming to bring to all of their properties.
Here is a before and after from Google:
Any ad design change with the Google AdSense ads is good because it stands out more, at least for the short term, until Google has to change it up to increase clicks again.
Forum discussion at Google+.