The problem with a check box that is either “checked” or “unchecked” is that you have no indication of a check box was intentionally left unchecked, or if an individually simply didn’t get to it yet.
I know right now you can set the default value of check boxes to by a formula "= " which leaves the check boxes kind of “grayed out”. This is nice, but the “grayed out” look doesn’t provide much of an indication for those who don’t know what to look for. If people don’t know to hit delete on the checkbox they might also have trouble turning these back to the ‘untouched’ state.
I would say to keep the double-state check box fields, but also add a triple-state check box field. If the triple-state checkbox has not been touched it will be a blank square. A Check mark indicates “Yes” or “true”, and an “X” over the box indicates “No” or “false”.
This would be helpful as I could replace a lot of three-selection lists that I have and help clean up the interface.