I've had a chance to drive with my wife's Garmin c340 GPS and have to amend my previous comments.
- Estimated Arrival Time - This feature is surprisingly accurate, and is a great feature for calling ahead when meeting people or for making restaurant reservations.
- This unit provides actual speed in the map mode. A good way to check the calibration of your speedometer or for use on a boat.
- The Garmin does find some short cuts I didn't know about.
- The Garmin is programmed with a preference for major highways. Interstate, US, and state highways are the preferred routes over local and county roads and highways, so it doesn't always pick the most efficient route.
- It is still a girlie device.