Thanks to Robert Hansen writing for iPhone Freak on 10/28/08 for the following review of Google Earth for the iPhone: (but first check out the You Tube Video from Google about how to download and use the app)
Google has recently released an iPhone and iPod touch version of GOOGLE EARTH. The newly released app is available for free and offers functionality similar to the desktop version. Initially I was a little skeptical on just how well this would perform on the iPhone, but after playing for a little while I can say that it not only performs well, but was also fun to use.
Google Earth for the iPhone allows users to browse the globe with your fingertips. It even has links to Wikipedia articles for select locations as well as over 8 million Panoramio photos. Using Google Earth is simple thanks to the touchscreen capability, users can move around by swiping your finger, then once you locate that spot you want to check out, you can then pinch to zoom in or zoom out. The app also takes advantage of the built-in accelerometer and allows you to tilt the screen and get a different view.
Additionally you can use the search field to narrow into a particular location, and even use the built-in Location Services of the iPhone to quickly zoom in on your current location.
Overall, I am not sure just how often I would use Google Earth, its fun to play with, but one thing it seems to be missing are the street names, which you would commonly find in Google Maps.