Check your iPhone or iPad for an update to the Google Earth app today. Version 7.0 of the free, universal app features tour guides of historic landmarks, as well as 3D flyovers of selected cities.
The flyovers beat Apple to the punch because a similar feature is going to appear in Apple's Maps app this fall as a part of iOS6.
Cities included in this update include Los Angeles, Boston, San Francisco, Geneva and Rome. More cities will be added in the near future. The 3D flyover feature requires an iPhone 4S or an iPad 2 or later.
While testing the rendering, I found the calculations required for 3D quite fast on my iPhone 4S and my new iPad. Rotations and changes in angle and elevation were smooth.
In contrast, rotating around buildings in the beta version of Apple Maps on iOS 6 was not quite as smooth, as the app would render some buildings as a wire mesh and then quickly fill in the detail when the movement stopped. Of course we're comparing the Apple beta to the Google release, and I would expect performance enhancements when the Apple app is released later this year.
There's absolutely no reason to not download the Google Maps upgrade and enjoy the sophisticated eye candy and depth the app provides to an increasing list of cities.
The app requires iOS4.3 or later, and is a 22.3 MB download.