The new user profile API will be a big help for admins, especially when combined with the existing shared contacts API. With the user profile API, "administrators can retrieve and update profile information for all users on a company domain, giving companies the option to provide rich user information to make it easier for employees to find and contact each other," says Florian Niemann, Engineer, Google Apps team.
In other words, global address books just became infinitely more manageable and useful for Google Apps users.
This means that when end users search through their contacts, not only will they see the contacts they've added manually and via replying to emails, but they will also automatically have access to the global address book to find the contact information of their co-workers.
Last, Google also updated the contacts user interface a little bit. As admins add new contact info to the global address list, it will automatically be pushed down to all users.
These changes are good news, especially for large organizations that have multiple locations.