On Sep, 14, I just downloaded and installed Google Earth 4.0.2080 beta. It has new version yesterday.
This time it is Google Earth 4.0.2091 now.
If you already have Google Earth 4.0.2080, you will not get update information by check update in the program.
You have to go to http://earth.google.com/index.html to download the full version to update it.
It is pretty good to have so quick updates.
It is not so good to update without notification in program.