My Legend Cx does all of these same problems. Usually putting me 30+ feet away from where i am supposed to be. Also, i will be instructed to move 20 feet north, then after doing so, i'll be instructed to move 45 feet south... and so on and so fourth, this makes for long days...
My Datum is on WGS84, my North Reference is True, my Lock On Road is set to OFF... I too have felt i was just GPS immature, but my fellow cacher has often out performed me with his Explorist 200, which makes me very sad...
Are there any more features i may have set in the wrong position? I keep setting up caches and getting responses like "this put me in the middle of a highway, but i found the cache due to the clues, try this for your coordinates.." which is not only embarrasing, but just plain old unsafe...