<< Excuse my ignorance but can someone explain the difference between the 310, the 330 and the Handspring Visor GPS module? Aren't they all basically the same? >>
The 310 is the basic GPS, which simply tells you your coordinates. To actually see where you are in a map, like what street you're driving on, you have to hook it up to a PC or PDA with mapping software. The 330 is a step up because it actually comes with maps so you don't need a pc for a trip for example.