One question, do all these models give you the reading when you start of "Accurate to within XXX feet) It's usually like 20 or so. I thought they were more accurate than that. When I backtracked to my house waypoint it was within 1.25 feet.
The accuracy indication is stating that the system estimates your are within "X" feet of the exact position reported. If you backtrack close t the same time to a waypoint you have saved, the position reported will be almost exactly the same. This is because within a short amount of time, the errors introduced into the system are about the same - satellite positional error, signal reflections, timeing, etc.
So, even though the position is reported as almost the same, you are still only within "X" feet of the actual position vs. what was reported.
Without using a WAAS ensable GPS receiver your accuracy is typically within 10 meters (33 ft). My unit (not WAAS enables usually shows somewhere between 15 and 20 ft. estimated accuracy.