The first thing you'll notice when you sign in to adCenter is a new look and feel. You'll also notice some new features, so check out our detailed feature review blog posts for further information. Improvements include:
Campaign Management: ability to pause and resume ads and keywords, geo-targeting enhancements, and improved performance reporting on the Ads page
Editorial Improvements: faster reviews, dynamic feedback about why ads and keywords were disapproved, and inline notification when dynamic text causes your ads to exceed character limits
User Management: if previously you were only able to have one user, now you can create multiple account users Content Ads (U.S. only): get keyword bid suggestions and performance estimates for your content ads
I think still a lot has to be done. For example the whole interface itself is boring to start with. Speed is another issue. Open Adwords in a tab and Adcenter in another and do the same exercise in both - the difference is visible. Still a drain - but cleaner!