GNU is a stable, powerful, flexible operating system that respects users' privacy and promotes freedom.
As any web administrator can tell you, the overwhelming majority of PCs run some version of the Microsoft Windows operating system, with Apple's Mac OS X (the Mac isn't usually referred to as a "PC" but it is) coming in a distant second, and all other OSes trailing far behind it. GNU (usually called "Linux" or, alternately, "GNU/Linux") has less than 2% of the market. Many Windows users are content with their OS and, with the rise of mobile computing (and a corresponding decrease in desktop use), most of them can't think of any good reasons to switch operating systems. Here are five reasons why you should make the switch today:
5. Stability & Security: With its roots in Unix's rock-solid design, GNU is impressively stable. Programs rarely crash and when they do it's usually a simple matter of a couple or mouse-clicks (or keystrokes) to kill them, before they take the system down. Also, updating the system and/or applications is a breeze and it is almost never necessary to reboot after you're done (updating the kernel is one exception).
GNU is refeshingly free of viruses and other malware. Because of design choices, in most cases, it is impossible for malware to install itself. This makes antivirus software and its concomitant hassles unnecessary. It also protects users from identity theft via trojans and saves users a lot of time in not having to re-install the system every few months.
4. Power: GNU is a powerful, expressive operating system that doesn't hide the internals of the system from the user. Users, who choose to, can remain blissfully unaware of the system's complexity, but those who wish to explore the system and unleash it's power, are free to do so in a multitude of ways: They can use the powerful and flexible shell to make the system do exactly what they want, plus they have access to the system's source code, so, with the right technical chops they are able to bend the system to their will.
3. Privacy: With the recent revelations of PRIZM, the government's program to spy on its citizens, it's nice to know that because of the free access to the source code many eyeballs are reviewing it, reducing the chance of the existence of code that monitors users behavior.
2. Cost: GNU is available for free, from multiple locations across the web. Most distributions have easy to use software installer/updater applications that make getting new software or upgrades a snap. Not having to shell out hundreds of dollars each time you want to upgrade your system -- or any of its applications -- is remarkably, well, freeing.
1. Freedom: GNU respects your freedom. The GNU General Public License ensures that your rights to use your computer, in the way that you see fit, is protected. It also secures your right to make any changes you'd like to the software, and to share those changes with others.
With all this going for it, why would you choose anything else?