Hello All -
Wanted to post my experience using a GPS with digital maps in the USA and last summer in Iceland.
My "out of the box" Garmin 60csx was a useful toy in that it showed that there was a highway some 50 miles away and that my truck was in that direction in relation to my present position. Against a beige background. Interesting, but not very helpful.
I then purchased the mapsource set of digital maps for the usa and a 2gb micro sd card and used them in Utah last spring. An amazing difference. I suddenly knew where I was, and where I wanted to go. I used the maps to locate and track my progress in canyons (for example, how far is the Colorado river (approximately), just around the bend or far away) and to bushwack back to roads. Even though the scale is 1:100,000? and the contours a bit wide I was surprised at how useful it was.
I then downloaded a free topo of Iceland which I used to hike the Laugauegurinn and Hornstrandir routes, amongst others. As I travel solo, I was concerned about not getting (very) lost, particularly in an area with few landmarks. Again, the GPS proved invaluable in helping in those few situations where the direction of the route was not clear due to snow, weather or where multiple routes intersect. Particularly important as I passed only 1 group each day. Again, even though the map was at a scale of 1:100,000 being able to pinpoint your position makes this scale very useful. Also being far north I had very good accuracy, often 1 meter or less.
Is GPS failsafe? Of course not. But it has proven to be a very useful tool and I find myself increasingly tossing it into my pack even on short hikes just like you would do with a map. I feel much more confident about being able to find my way around other countries and the way back. Hopefully it will be as useful in Argentina this winter.