the best feature of Google Earth...
..is image overlay. Way Way Cool. I can take scanned geology maps and lay them on the terrain. Then I can adjust the transparancy of the image. I've also been overlaying the maps I generate in AutoCad: claim maps, topo maps, geology...It makes for a really nice presentation.
Just one thing, it'd be nice to chose rotating around a spot or rotating from a fixed location (the later is not available.)