Free, powerful, highly customizable, fast, diverse, and constantly developing--what more can you want in an operating system? Linux is definitely the operating of choice for power users and administrators alike.
The biggest factors that affect Linux's adoption rate is hardware support, and user experience. Granted, many distributions now ship with incredibly good GUIs, the core of the operating system still remains very much like it has always been. Although more and more devices ship with Linux as the OS of choice, Linux's market share remains tiny compared to that of Windows and even OS X (based on BSD).
I have a Linux machine at home, that I use for firewalling, file serving, and other things, but it doesn't have a GUI installed. This is primarily because all the box does is serve. It wasn't built to be a desktop machine. Service layers however, remain Linux's primary focus. To access the box, I terminal in using SSH from another machine. The machine can be entirely managed through the terminal.
The question of the day is: Do you use Linux/BSD with a graphics user interface?
Or do you use linux primarily for services?
