Have been experimenting with a number of walk tracking methods on my IPhone. There are many pedometer style applications, which work fine but need calibration. Now that I have a GPS phone have looked at several GPS applications as well. Installed MotionX GPS. Cheap at $2.99 from the App store and works well. It has a hard time acquiring a satellite indoors, while my Garmin gathers an indoor signal readily. It overlays any path you take onto a set of open source street and topo maps.
Accuracy is very good, very similar to my Garmin, it readily tracked which side of a suburban road I was walking on. Has a virtual compass, route management and sharing software, waypoint analysis, timing, etc. You can take pictures with the phone, then associate them with a waypoint and send the pictures via email to record your trip. Does not have turn-by-turn directions, not meant to replace a car GPS. I figured the interface out fairly quickly. Only problem discovered so far is that the GPS drains the IPhone battery quickly. So may not be good for a very long hike in the woods. I will be doing some tests on my usual round-the-lake walks in the coming days.