It's interesting to hear so many different opinions on the command line. Many see it as archaic. Others are scared of it. And then there's a few who prefer it to all other interfaces. But regardless of how you feel about it, there's no denying that it's here to stay, at least for the near future.
I've mentioned earlier that interacting with a computer can be likened to communicating with it. We usually "speak" to it in the physical sense through a keyboard or mouse. On the virtual or software side of things, the most popular interfaces are either through the command line, or a gui (wimp interface).
Command line interfaces allow for more direct communication with the computer. You type words that you want the computer to execute, and it returns the response. Going through a gui is like talking to an interpreter first, and then having the interpreter relay the information. This can be more useful if the interpreter can figure out what you mean and make a more informed request to the computer. But for informed users, interpreters just get in the way.
Where I think the command line really shines is its flexibility. At a moment's notice, you have access to virtually anything, all through a single interface. You have access to a large, powerful set of tools that can be widely used with one another. For example, what if I wanted to count the number of files in a directory that had an odd number of lines in them? That were edited in the last week. And have those sent out in an email. Biweekly. Granted, that's a contrived example off the top of my head, but one that is virtually effortless to accomplish from the command line, yet difficult with a gui that wasn't designed specifically for that.
Another useful feature of the command line is its inherent repeatability. Once a command has been run, it can be recalled, executed as is, or executed with slight variations, all with little effort. This is true for sequences of commands as well. And, if the sequences themselves start repeating in sequence, then they can be moved to a shellscript or function and run with a single command. In this way, the command line allows for the user to create new language that is better suited for the problem, in a bottom up approach.
Guis have their place too though. The knowledge required is usually much lower to start being effective with an application. And guis are a better fit to solve visual problems. It's much easier to work with a wysiwyg type app when you're producing a new design, rather than having to perform transforms with commands and then redisplaying.
But I think the audience is what makes the biggest difference. Programmers, and "expert users" have a tendency to prefer command line tools. Novice users are usually afraid of having something go wrong, and find comfort with gui applications. And for the die hard gui guys, all you have to do is tell them:
Smith and Wesson was the original point and click interface