If you have tried GE3, or even played around with the earlier releases of GE4, it's worth it to get the full upgrade. There are a huge number of interesting updates, including Blue Marble, a real color overlay that makes the planet look better and more realistic, more layers, improved handeling of the layers so the large data points don't grind your computer to a halt, much improved 3D buildings and terrain, time slider capability to show changes to areas, and a bunch of other very interesting things.

GE is very important to me as I use it as a plotting tool for SailBlogs. Many of the blogs have direct ties into GE to show their blog entries and photos on a geographical basis. The above shows the positions of reporting boats, for example (except you can't see the icons...). Clicking the little icon takes you to their blog.

There are so many cool things to do with Google Earth that I can't even begin to list them all here - I personally follow the Google Earth Blog to keep up to date. Frank was very kind to feature SailBlogs after I got the feeds working, and that has lead to a lot of good traffic for the sailing site.

The whole concept of Google Earth is amazingly simple. Its far more than just sat photos. Its 'lets take a planet, and overlay it with anything, anything at all, that is geographically based - any map, any location, any photo, and use this virtual planet to browse it and combine it with other maps and data as well."

Its just amazing.

download it here