Being a dedicated Firefox user, one of the few things that was still thwarting me was SharePoint. We use SharePoint internally for a ton of stuff, and it was a drag to have to fall back to that other browser. SharePoint pages look and work fine in Firefox, but I was having to reauthenticate on every single page, which really hindered my enjoyment of the experience.
I finally figured out how to get Firefox to do NTLM, which means I don’t have to deal with the authentication dialogs, thereby reducing my dependence on IE
I am an advocate of centralized identity management and I think Active Directory makes a great repository for user account information. Interoperability can be a challenge, though. For example, you may work in a mixed environment of Linux/Unix and Windows and want users to take advantage of their Windows accounts when logging on at a Linux/Unix machine. This provides single sign-on for users who otherwise would need to maintain two different sets of passwords.