I've never had any issues with GPS. The units I have work well for me.
That said, I alway carry a map and compass with me in the backcountry and I know how to use them.
I teach backcountry navigation classes in the Pacific Northwest.
I try to impress on my students that land navigation skills are on a par with and just as important as marksmanship, tracking and physical condidtioning.
Blake
www.outdoorquest.bizwww.outdoorquest.blogspot.com