Google announced even more improvements to the ad review center which launched back in 2007 and has been getting continued improvements over the years.
The latest upgrade is three fold:
(1) Ad Reviews Center Impressions-Based Progress Bar
(2) Ad Previews, Landing Pages & Quicker Blocking Access
(3) Ability To Block Visually Similar Ads Via Screenshot Upload
Ad Reviews Center Impressions-Based Progress Bar
Here is a picture of the progress bar, which shows you the total coverage of the ads you have reviewed so far. This new feature tells you the percentage of ads you have reviewed relative to the total impressions on your site.
Ad Previews, Landing Pages & Quicker Blocking Access
You now have access to information on a specific ad simply by hovering over the creative and clicking on the magnifying glass in the bottom right corner:
Plus, you can click on the magnifying glass to preview the landing page:
Ability To Block Visually Similar Ads Via Screenshot Upload
This feature I did not see live yet in my account but Google describes it as a method of using Google's Image Search feature to review and block visually similar ads by simply uploading a screenshot or logo, or searching for text in images.
Forum discussion at WebmasterWorld and Google+.