Gmail's faster, more flexible new codebase is now becoming generally available to Google Apps users. This change brings a faster interface and several new features including group chat from the browser, a streamlined contact manager, colored message labels, improved keyboard shortcuts and bookmarkable messages and searches.

Editions impacted:
Standard, Premier and Education Editions

Languages impacted:
US English

How to access what's new:
Just sign in to Gmail. You'll know when you're in new version of Gmail when you see a link for "Older version" at the top right of the screen.

For more information:
http://www.google.com/a/help/intl/en/users/gmail.html