I'm able to go directly to the Windows Update site by clicking Tools->Windows Update in Firefox, using this extension.  It does exactly what I want it to do.

The WindowsUpdate extension opens IE to the windowsupdate site.  It doesn't open it within Firefox, unless you have the IETab extension installed.

I've admitted all along that it isn't useful for people that know their way around a computer.  It wasn't written with those people in mind.  I know many, many people who wouldn't know how to get to the Windows Update site unless they pulled down Tools->Windows Update from IE.  I wrote this extension to give those users the same familiarity within Firefox.

I've honestly taken a lot of crap from people on the addons.mozilla.org site (read the comments for this extension there!), and it's disappointing.  "No good deed goes unpunished" comes to mind.

=)