Originally Posted by gastro
Believe what you want to...just because your receiver tells you a position doesn't mean it's correct.
These are not survey-grade instruments. But no one needs sub-meter accuracy for mountain biking, do they? The only real objective is to follow a route or determine a speed. If the thing is giving me the position for a known object (either from a previous waypoint or a geo-referenced map) and I am standing next to said object, I think that is correct enough for most user's purposes.
In the last three years there have only been three or four times that my GPS actually claimed that I was somewhere I wasn't (i.e. showing my location on a built-in map) and the errors were corrected after a second or two. Otherwise, the thing tends to be as good as any of the maps I have.