For me personally this could be quite useful in my job. I am in the mapping industry and create/receive a lot of custom KML/KMZ files. If this app has the ability to view said files (especially from email attachments) then that would be great for field work and quick viewing to coworkers and clients.
Can someone tell me exactly what "real world" purposes Google Earth serves that aren't already covered by Google Maps?
Ok, does it have any use to anyone NOT in the mapping industry? Or is it just something cool like Google Sky?