As of April 16, 2013 the redesigned compose and reply features in New School Google Apps, released in October 2012, are now enabled by default for all users.
You can opt out of the redesigned compose and reply features until they're permanently enabled on April 30, 2013. If you opt out, you can opt back in at any time.
To learn more about this feature, refer to the Google Apps Learning Center, which includes an overview and user guide.
If you are not yet familiar with this new feature, please take a moment to review the video embedded above.