The command line interface (CLI), for those who are not familiar with it, is the (scary?) thing you see on your computer's screen full of text that is mostly gibberish to the untrained. Those who are familiar with it may argue with me because they are so comfortable with this type of computer interface. Actually, CLI is not bad for the user's experience all the time, but it generally is. As I implied earlier, it requires training (usually a lot of it). Without a manual or any sort of guide, operating it is nearly impossible. To be fair, every type of interface needs some kind of guide to the user, but the ones with the better design require much less education and are usually easy to understand for most people because they do not deviate very much from the conventions of other things that people interact with.
Some of the reasons why some love the CLI are their familiarity with it, the speed of operating with it compared to the graphical user interface (GUI), and the things they can do with it that they can't with the GUI. However, the graphical interface is becoming faster and more feature-rich. Moving, copying, and opening files are among the most popular activities done on the CLI. Applications like Quicksilver (for OS X) and GNOME-Do (for Linux) can execute those commands even faster than on the CLI. Those applications are more ubiquitous than the terminal or an emulator, in most cases. Because of their accessibility and speed of execution of actions (like moving, copying, and opening files), they are more practical for more people than the CLI because of their presentability, learnability, and better User Experience design in general. In Linux, many power users are inclined to manage their software through the CLI. Thanks to Ubuntu, the Software Center serves a great GUI to manage software for new and expert users. It is so fast and smooth that it could be more practical than the CLI even for power users.
Graphical interfaces made by different parties, like CLIs of different platforms, usually have varied conventions, so new users of both kinds of interface will always have to learn new things if they are not limited to one perfectly consistent platform. What makes the GUI better than the CLI is its learnability. Let's face it. CLIs, at least the ones available today, always need manuals and they do much more than most GUIs.
Despite the points I mentioned, there will always be people who will have a good experience with the command line. This may be funny for most people, but some computer experts just love to see things happening in such a geeky way. The CLI is actually positively affective to a special breed of people.
To sum it up, having fast and feature-rich GUIs are much better than CLIs for most people, because of their richer capability of being designed for the human being.
Thoughts on People and Technologies that Extend Them