In some cases the firing of the OnChange events seem a bit off. The event is not triggered until you tab out or select another field on the form. While this works well for text fields since you may not want to trigger the event until you are done typing it does not seem to be optimal for some of the other fields. In particular onChange scripts attached to two options checkbox fields really seem off. People are just used to seeing actions take place when they select a checkbox, not when they move to the next field. If you have an form script that is linked to multiple checkbox fields it really gets weird for users as it seems like the script is onClick behind them.