Frankly, we don't know why we didn't see this coming. The iPhone has a pretty solid mobile 3D chip, loads of caching space, GPS and an awesome touch interface. All perfect for a mobile version of Google Earth.
The app is pretty solid but a little clunky to start up. It does include Panaramio pictures, Wikipedia entries that are geotagged and bunch of other nice stuff. We do get a pretty consistant crash when we try to move after a GPS lookup - your mileage may vary.
