iPad Hardware FAQ: what are differences between the iPad Wi-Fi and iPad 3G models?

Besides price, there are a few physical differences. The iPad 3G models weigh an extra tenth of pound, and have a black antenna window that covers part of the top and stretches onto the back of the iPad. The iPad 3G models also include GPS functionality.
The iPad 3G models also cost more than the iPad Wifi (wi-fi) models.