In response to your original post, North, I bought a Quest as it is waterproof to a point, hence good for the bike and as a hand held unit. It is clear enough for the car provided you are not blind or that your dash board is not 3 ft deep. Another added bonus and sort of essential if it is to be used handheld is the internal battery as well as its direct power connection once in its cradle.
However, it gives you no idea of the lie of the land, only roads and points of interest (although it will tell you your existing elevation) so you can't look around and say "I have a peak to my left and one in front and so I must be here" etc.
I know little of orienteering, but I agree with the wisdom of not relying wholly on one means, so if you've got a compass, a map, radioactive breadcrumps and a geiger counter as well, I'm sure the Quest won't lead you astray. It also has a trac-back facility which will direct you along the route you have just walked, unless this is up the cliff you have just fallen down, in which case its less helpful...HTH