GeoTagging is cool. I've been using the MS Research stuff to do it on Windows, however I've recently switched to a Mac, and am still searching for a good solution.
The Eye-Fi isn't exactly doing GeoTagging. It's pulling your location data from an online database of WiFi Accesspoints called
Skyhook.
That's not exactly going to work when you're trying to remember if you took that shot from the North or South rim of the Grand Canyon.