A WebmasterWorld thread says Microsoft is inviting some adCenter advertisers to beta test a new ad editor. The acronym for this product is ACE, standing for adCenter Editor (Beta).
According to the member in the thread, it appears to be an Internet Explorer browser plugin that helps you manage your search ads. I assume it speeds up the process as well as gives you more data as you edit them.
Here is the exact post from WebmasterWorld:
I just got an invite to try the beta version of the software called AdCenter Ace.
If you have firefox set as your default browser you may have trouble installing this program. I had to make IE my default browser to install Adcenter Ace :)
Hopefully it will become a bit easier to use AdCenter.
I don't have official confirmation from Microsoft on this new beta nor do I have screen captures at this moment.
Forum discussion at WebmasterWorld.