I've only used terrabrowser without connecting a GPS unit (but have found out how to make my Magellan Explorist 300 connectable elsewhere) and have been satisfied with the performance of this utilitarian application.

I have one caution for those out there naming their waypoints (and who doesn't?)

Do not use the ampersand (&) symbol, for some reason it renders your bookmarks unreadable and it'll appear as if you've lost them all on your next launch.

Furthermore it renders Terrabrowser unable to add further bookmarks to the file.