Lance,
As far as the cost for the Garmin 478 goes it is whatever the market will bear. Since they haven't been in production for a while combined with the insane cult like following the price is going up on sites like ebay. Loyal followers on sites like
www.advrider.com are buying a backup for when theirs eventually die. I was introduced to the Garmin 276c by Graham on our Central America trip. I really liked the you could customize screens on the fly, screen size and the interface. After getting back and learning that virtually any map you ever wanted is available for the Garmins that use the mapsource software I was sold. What really closed the deal for me was the "Baja Navigator" map being available for download on the Garmins. After downloading the Baja Navigator map I'm blown away at the level of detail. For instance when I leave the hot springs at Canyon de Guadeloupe which is in the middle of a huge dry lake bed/desert all of the dirt track and Baja 1000 routes are on the map for me to choose from as I'm continuing south.
While in AR this week with the family my son and I have started geocaching with the Garmin 478 since it has a 10+ hour battery in it, very versatile. The Garmin 478 can go from your auto to boat to motorcycle and never blink an eye.