Garmin GPS under Ubuntu is not a problem
My Garmin CSx 60 works like a charm with Ubuntu Karmic 9.10 after doing modprobe garmin_gps to make kernel to see the garmin protocol (for using with MapSource).
Mapsource also works well under wine after trick with symlinking usb to serial. Guide how to install MapSource was found here.
Here is page of MapSource and Wine compatibility. Current version requires some of winetricks to be done: vcrun2005 and corefonts.
Also noted several nice and useful (even better in some aspects then closed analogues) open-source programs for working with GIS data: QLandKarte and JOSM for editing Open Street Map maps.
Next step is may be trying to use OSM maps instead of Garmin ones when coverage and quality allows.
