Deciding whether to use a particular extension or not is a Systems Integration process -- you first have to have a need that a given extension is a fit for. So using extensions is about meeting existing needs, not about providing eye-candy or cool toys.
In general, customisation of Mozilla is a highly useful activity for sysadmins, provide that you have a little time. Because the whole of Mozilla's interface is supplied as plain text files, it is very easy to "harden" the application by subtracting away features that you don't want. That is the opposite of adding extensions. Similarly, it is possible to enhance the interface as extensions do.
Once you've made your changes, it is also easy to bundle up the results into a fully installable package.
Mozilla's XUL is the technology required for extensions, and that technology I've only touched lightly on here. XUL is a good way to wrap up any command-line sys admin task into a nice GUI window. Such a GUI window is easy to operate once it's built. WebMin could be enhanced to work that way, for example.
Using XUL requires more effort than merely dropping in an existing extension, though. Perl or Web skills are ideally required.
This was first published in April 2004