I consider myself well versed in the KML format since I just implemented most of it's features, and found them to be needing much more in the way of styling. KML will now change at a glacial rate due to the standards process, right when it needs to change the most! Google Earth's feature set will now become dictated by an outside entity, with their input of course, but that's no way to develop software! Why would they cripple Google Earth like that?
Also libkml has been released and it was exactly what I thought it would be, a glorified xml validation script for the kml dialect. I predict that no significant software will choose to link that library in.
I have to say the lamest thing about KML is the whole Style/StyleMap tag collection that enables one to set a separate style on an icon for mouse-over events. It's a great way to have a non-standardized interface since everyone rolls their own mouse-over effect for each placemark style!
I've implemented a few of my own extensions to the KML format which I will go into detail about later. They are mostly aimed at visibility and styling extensions. One of the most useful extensions is the