I use QLandkarteGT on Linux to access my Garmin Venture HC GPS. All things considered, it works pretty well. I recently upgraded my computer to Ubuntu 12.04 and it stopped communicating with my GPS though, and I was very sad. The error was "Failed to download waypoints. Failed to configure USB: could not set config 1: Operation not permitted." After tinkering with it I remembered that the way I fixed it before was by setting qlandkartegt to run suid root.