I've been trying to get Firefox reeady for deployment everywhere in our organization. Here's one less thing to workaround: Integrated Windows Authentication in Firefox. Basically I just needed to add/modify the following values:
network.automatic-ntlm-auth.trusted-uris = intranet
network.negotiate-auth.delegation-uris = intranet
network.negotiate-auth.trusted-uris = intranet
This allowed my to browse straight to http://intranet/ without logging in.
You can add more domains to each setting with comma-separated domains.