Old scoop, Jack! Navionics' web site says "Garmin used to license
Navionics cartography data and formatted their own chips sold as G-
Charts. Garmin now uses their own cartography." That happened when
they came out with BlueCharts several years ago. Navionics tripled
what they were charging Garmin. They are not friends anymore.

I use mapsource to generate and move waypoints among all my Garmin
GPS', from my Etrex to my 162, my 182C, my 3010C and my 4208. I also
used i to put some routes and waypoints into a friends new 545, a very
sweet unit!

Yes, its easier to create good waypoints and routes when you have
purchased charts for your PC, such as the BlueChart CD (9.5 is the
latest version) but you can also use Mapsource to open *.gpx routes
and load them to the GPSs. A free ride is available with a demo
version of Coastal Explorer and a download of Free NOAA charts. Where
I used to need Garmin's proprietary chip reader, still available for
$60 for all Garmin's previous (pre 2007) GPSs, the new units use SD
memory cards. I bought a 2 gig chip and reader at Best Buy for $24!.