Yes, we also carry a magnetic compass--but haven't used it in years. We really could not get along without the electronic compass. We get erroneous direction pointing from time to time, but usually only when we are within a few yards of the sought target. We've found under those circumstances: slow down, stop. Let the "arrow" stabilize. If we do not spot the cache quickly, we change from the compass page to the coordinates page and place a marker at the spot where the cache page coordinates match our gps'r indicated coordinates. When those two numbers match, don't chase the needle, look for the cache. We then turn the unit off and conduct our search. That has worked for us.
Yes you do need to calibrate the electronic compass occasionally--takes 15 seconds.
I guess we're sissies--really appreciate WAAS--and remember the good ole days of SA's 25 meter allowed accuracy!
We don't need no stinkin' magnetic compass, we always carry extra batteries and an extra gps'r.