From the Google Lat Long Blog:
Google Earth Pro has all the easy-to-use features and detailed imagery of Google Earth, along with advanced tools that help you measure 3D buildings, print high-resolution images for presentations or reports, and record HD movies of your virtual flights around the world.
Starting today, even more people will be able to access Google Earth Pro: we’re making it available for free. To see what Earth Pro can do for you—or to just have fun flying around the world—grab a free key and download Earth Pro today. If you’re an existing user, your key will continue to work with no changes required.