In order to obtain the feature, you simply upgrade to the latest Google Earth. This adds a ‘sky’ button to the toolbar which looks like a graphic of Saturn.
My first impressions are mixed. I like Stellarium and Celestia, and I’m probably not going to stop using them in favor of Google Earth for two significant reasons: 1) Google Earth requires a live broadband Internet connection, which is something I typically don’t have the luxury of at my usual observing site, and 2) Google Earth’s pictures of the sky are visibly stitched together, especially in the region around Polaris. Take a look at this picture, it is the region around polaris, and it looks like it’s supposed to be a meteor shower radiant. If you zoom in on that section what you see is blurred, smeared objects instead of nicely rendered pictures.
Having said that, the interface is intuitive, and if you are familiar with Google Earth it is easy to move around in it, find interesting objects, and zoom in on them. The data appears to be coming from the Sloan Digital Sky Survey, and some of the pictures are impressive. However, there are many visible ‘stitching’ lines across the views, which are distracting.
As a tool that introduces some basic astronomy concepts, it’s cool. However, as a tool for use by anything more than the greenest amateur it falls short.