<Logs off from The Elder Scrolls IV: Oblivion> Yes, ahem, you can’t play games on Linux.
Linux is an operating system kernel. On top of it, many companies build full-fledged operating systems. With little exception, they are all completely free and open source.
Perhaps 5 years ago, Linux would not have been a viable option for the average computer user who just wants something to browse the web and recognize their printer. Today, modern distributions such as Ubuntu, Mint, Fedora, and OpeneSUSE make Linux very easy to pick up and run with. These distros are making an attempt (successfully) to appeal to a broad range of computer users.
For instance, Ubuntu (the distro I use), comes pre-packaged with Firefox, Open Office, Evolution (mail client), Pidgin (IM client), Transmission (torrent client), GIMP (photoshop alternative), as well as software to play music, videos, and the like. For any average user, anything you might need on a daily basis already comes pre-installed. No hassle.
On top of that, all software on your system self-updates automatically. You don’t have to worry about keeping up to date with the latest versions of your software, your system will update everything for you.
Software on Linux is also (for the most part) easier to install than on Windows. Instead of searching for a website, downloading an installer, running the installer, and hitting “next” a bunch of times, each distro comes with a package manager. You just search for what you want, check a box, and it does the rest for you.
You will never have to worry about security with Linux. Not only are there almost no viruses or spyware for Linux, even if there were, it wouldn’t much matter. Linux is far more secure than Windows. You never have to run any anti-virus programs or firewalls.
Linux is completely customizable. Windows lets you change a few settings here and there, but in the end you pretty much always end up with a system that looks exactly the same. In Linux, you can make your desktop look however you want, with almost no limitation. Seriously, I can’t stress this enough. There are countless themes and icon sets for you to use, and everything can be changed to your liking.
Linux will be faster than Windows. Not 10 times faster, but noticeably faster. It will boot and shut down quicker, and it won’t slow down over time as much as Windows does.
Now, there are some cons. First of all, as TCH alluded to, you probably should avoid Linux if you are a hardcore gamer. Games are made for Windows; that being said, the Wine project works towards letting you run Windows programs in Linux, including games. Like I said earlier, I just finished playing Oblivion. However, usually using programs in wine takes a bit of messing around and the quality is often reduced. If you have any games or programs you absolutely need to use, and absolutely have no Linux alternative, you should check that link to see if you can run it well with Wine.
Fortunately, there are some great ways to try Linux without committing to it. Most distros use a Live CD installer, meaning that you can boot into the operating system straight from the CD without installing it to your hard drive. You can use it for a bit to see if you like it. If you don’t, just pop out the CD. If you do, you can install it straight from within the CD. Alternatively, if you are interested in Ubuntu, there is a fantastic application called Wubi, which installs Ubuntu from within Windows. This way you can have both Ubuntu and Windows on your PC, allowing you to choose which one you want to use when you boot up. If you decide you don’t like Ubuntu, you can just uninstall Wubi from within Windows, and it will be erased.
And again, it’s absolutely free for life.
If you have any other questions, please feel free to ask. I recommend checking out some random youtube videos. There are countless videos of people showing off their customize desktops. Search for something like “Ubuntu Compiz Fusion.”