When new Google features are introduced, normal Google users get them right away, but Google Apps user accounts may be set to a scheduled release track, which delays the rollout of new features.
If you want new Google features to propagate immediately to your Apps accounts, you'll need to change the release track from Scheduled to Rapid Release. Here's how:
Log in to your Google Apps control panel and go to Domain settings > General. Scroll down to New User Features and change the selection from Scheduled Release to Rapid Release.
If you don't want to have to approve new features manually, make sure that New Services is set to Automatic, rather than Manual.
That's it. Now when you read about that great new Gmail feature, like How to replace the Gmail icon buttons with text buttons, your Google Apps accounts will get them right away.