So many ways to check if a checkbox is (not) checked :) especially if you mix in a little jQuery
...and the winner is:
http://jsperf.com/not-checked-vs-not-checked
...and the winner is:
!$('#my-test-checkbox')[0].checked
even though i like to read
$('#my-test-checkbox').is(':not(:checked)')
http://jsperf.com/not-checked-vs-not-checked