Initially, the layout of medium and large rectangles, and the leader board changed.
Leader Board (728x90)
The title, description and URL after the update is no longer in a column view, but in addition together.
Rectangles (300x250 and 336x280)
The URL has moved and is now directly behind the title. Previously it was on a separate row below the title and description. Google indicates that in some cases the font is adjusted to the texts easier to read. The changes will be within a few weeks in each country were conducted.
Google AdSense will not be available for some time until the changes has been made in the system, so we have to be a little patient. But when Google’s did testing the redesigned ads it performed extremely well.
You can read more on Google's Inside AdSense Blog