If you're standing still how does the Maggie know which direction you're facing? How does avg'ing make the pointer anymore stable than a garmin?
It's not when you are standing still. With the Garmin, if you are walking across a field towards a wooded area the pointer jumps widely across a span of as much a 90 degrees -- anywhere up to 45 to the left to 45 to the right. I believe this is because it is changing to it's latest calculated position. (I don't know this, I just presume it.) On my Maggie this swing is damped by averaging, so it is more like 10-20 degrees left to right. On the Garmin I try to mentally average the jumping around, but on the Maggie I just follow the pointer. As Ms Muddy Buddies mentioned this jumping around gets worse in the woods.
Another situation is when the unit is in one location and I'm trying to use the bearing. After the Maggie is in one place for a while the averaging makes the bearing settle down to a fairly consistent direction. The Garmin continues to jump all over the place making the use of a bearing and compass almost unworkable.
I'm sure that shortens battery life a bit.
It does. The battery life on the Garmin is much better.