Google has just released Google Earth version 5.1. According to the LatLong blog, the focus of this update was speed.
According to Google:
We’ve made a lot of adjustments under the hood, like improving memory utilization so we can show more buildings, layers, and user content. We improved our shaders (that’s graphics-speak for small programs that run inside your graphics processor) to make the atmosphere draw faster. We also worked to reduce stuttering (known as frame drops) to provide an even smoother experience as you fly around the globe. When we draw imagery, we now use compression technology to use less memory and graphics resources. We know that waiting for a program to start-up can be really frustrating, so we improved our start-up time by 25%. In our Google Earth API (which allows developers to include Google Earth right in their websites), we have made API calls significantly faster, which means that our developers can now do even more.
You can download version 5.1 here. In addition, the Windows version of 5.1 automatically loads the browser plug-in for those users, which should signifianctly increase the number of users that have the plug-in installed.