So I have been thinking of using my iPhone on 4x4 trips instead of a dedicated GPS (a la Garmin)... I know that the app I use would have to cache topo maps ahead of time since I can't count on 3G signal. I've played with GPS kit, MotionX and Tracker, but I'm not convinced that these programs would really cut it to replace a dedicated device.
Have any of you tried using the iPhone as you primary off road GPS? What app(s) do you prefer?