I just noticed it so i thought i should blog it as well, not sure exactly when it was released but its here.

what it does is give your ad unites a unique ID and you can manage these ads in the adsense ads slot, mostly its about colors only since size is specified within the ad code that is added to the site, this feature is to increase CTR by changing colors of the ads from time to time, a little change can certainly increase CTR.

Also i find this a better way to manage ad units on my sites.

Edit: Apparently this was announced on the 5th of november on the google adsense blog.