Your post reminded me to update the maps on my Navigon. About seven weeks ago there was a screaming deal online that allowed you twelve quarterly map updates, for about $25.
I'm downloading the most recent update right now on a 2.5MB line, and I'm going to guess it will take about two hours to complete the whole process. The unit only has 2GB of internal memory.
Not surprised the Garmin takes forever to update. BTW, both Garmin and Navigon I believe use the same basic NAVTEQ map set.