That is my only complaint about the compass, it seems to require constant recalibration. For a quick and dirty reference though (particularly when I am hunting (archery)), I find it pretty useful. It can't replace a good ol' fashioned map and traditional compass but it can be, as you said, a great backup - especially if you have passable orienteering skills.
The thermometer is absolutely not accurate unless you have it off your wrist for a few minutes. I don't like wearing my watch at night - even while out in the wilderness - so I loop it on the ridgeline of my shelter right above my head. This way I get a good temp reading in the evening and morning - if I am curious throughout the day, I'll take it off but honestly, I very rarely do that (too busy with other stuff).
Probably should throw in another pic to avoid too much drift.