+1 to Joern's suggested patch - I definitely agree that checking if the element is visible makes more sense.
Concerning the 'visible, enabled elements' tests failing for the 'area with href' case, I've noticed that these <area> elements consistently have an offsetWidth and offsetHeight of 0. I believe this is because the test map doesn't have any <img usemap=""/> relationships attached to it, so all of its internal <area>s are essentially hidden. jQuery 1.3.2 checks for a positive offsetWidth or offsetHeight in its implementation of the ':visible' selector and so this is what causes that subtest to fail.
However, the <map> parent should still have a valid width/height, and the following tweak to Joern's suggest patch causes all of the 'visible, enabled elements' tests to pass 100% in Firefox 2/3:
&& ('area' == nodeName
The problem is that the same is not true for either Chrome or IE 7. They both consistently report that the <map> and all nested <area>s have an offsetWidth/offsetHeight of 0, causing the is(':visible') check to report false every time.