I'm getting quite a few hits on this entry from search engines, so I thought I would add some information:
I purchased EarthViewer 3D, but not the 'Pro' version from Keyhole. Keyhole and Nvidia have a special package for people with Nvidia brand video cards (GeForce or later is required). You can read about it at Keyhole's web site. It has most all the features of the 'Pro' version for a small fraction of the cost. It's still a yearly subscription, but consumer priced.
My guess is that the spike in searches for 'earthviewer' is due to the Iraq war that's happening as of this update. Please note that Earthviewer does not provide realtime viewing through satellites or anything so glamarous. The pictures you see have been taken in the past -- sometimes from years ago. They are downloaded from KeyHole's servers in realtime -- meaning, you don't have all of this imagery stored on your computer. This also means that you need a broadband Internet connection for the application to work reasonably well. Maybe 10 years from now we'll have a realtime version of software like this.
I've been pretty happy with the personal edition of EarthViewer. Try out their demo and see for yourself.- - -
Keyhole's EarthViewer 3D provides a breathtaking view of our little blue-green sphere. You can pan, rotate and zoom the globe to your heart's delight.
I recall years ago seeing this kind of thing predicted on some PBS program-- they demonstrated what it would be like using very crude vector graphics. This is much, much better-- all photo based from satellite imagery. They can also project the terrain in 3D and highlight roads and businesses too.
The software (and service-- since imagery is downloaded in realtime as you move around the world) is $599 a year for professionals-- their FAQ suggests that they are making a version targetted at the average consumer. What a great way to learn your geography! Or find the way from here to there, wherever there might be.
Warning: running the trial will eat up a good deal of your time if you're not careful. I've been playing with it for a couple of hours...