Personally, unless it starts to cause probelms in game I could care less about minor errors on character sheets. The errors tend to work both ways, for and against the PCs, so it evens out. When my players level up I glance over their sheets and look for things I think they might miss, but I don't go over it with a fine tooth comb. Sometimes this means that later we discover errors.
My wife, however, constantly checks and rechecks her character sheet (in one game she is currently an 11th level High Dex Rapier Wielding fighter) and frequently changes things because she missed an applicable feat or add in the wrong number. It bothers her, and occaisionally it bothers other players (particularly when she does it in game and realizes a mistake), but she is more worried about being RIGHT than anythign else. Then we have another player who gets focused on her ability to do one thing that she forgets the other, like rolling sneak attack damage and then forgeting to add in the damage of her actual weapon. This is the first time this group has played at the midrange levels where things start to get complicated so things are bound to happen.
I am playing with friends, all of whom have such a high since of righteousness and fairness that it can be disgusting. If I was playing with people I didn't know that well, particuallarly when a game got to higher levels, I might be more inclined to audit the sheets.
