First, the export menu now has two Earth options - the traditional KML file, and a KML network link, which provides for automatic syncing between Earth and your CalTopo map. When you open the network link file in Earth, changes get pulled from CalTopo every 10 seconds - move a marker or draw a new line, and boom, it will appear in Earth within seconds.
Data only syncs one direction; changes made in Earth will not be picked up by CalTopo.
The second big change is better layer integration. I've always provided a few "super overlay" files for loading topos into Earth, but it was an obscure feature limited to a handful of layers. Now, basic and pro subscribers have access to an improved file, located on the account tab of the account dialog.
Download this file, open it in Earth, and you can pull in a wide variety of CalTopo layers, including previously-inaccessible transparent ones.
A few examples:
|Desolation Wilderness with the MapBuilder Overlay layer|
|Slope angle shading on a popular Tahoe backcountry ski spot|
|Public/private land boundaries|