The idea that command line is slower is totally unfounded. Research shows that if a person knows how to type correctly, and the commands they are using are intuitive, it can be many times faster than even the best designed GUI.

Lets use a file manager as an example.

If I want to get a listing of all the files starting with F in c:\windows\system using a GUI, I have to open up the My Computer window, find the icon for Windows, and open that up. Then I have to find the icon for System. Now, assuming my file manager supports pattern matching, I have to go to a menu, select "Filter", enter in the filter I want (in this case "F*"), and hit OK.

Now lets do it using the command line. "dir c:\windows\system\F*.*". That's all you need. CLI's are great assuming you know what you are doing. And even if you don't, you can use tab completion as a crutch.

Personally, I think the largest reason why people prefer GUI's is because they lead you along. It's the whole wizard concept. People like being presented with a list of options. They don't like to have to think too much.