Debian/GNU Linux is a free operating system, which anyone can use and which offers a most comprehensive choice of software for all needs. I've been using it for less than one month as of now (4 October 2005), and I'm quite happy with it. It's not too difficult to use it, it used to be, but nowadays you have the choice to use either the KDE or the GNOME desktop environment which give you the possibility to use all the feats a Windows OS would give you, without ever using the command line. Then if you want to start experimenting and know your computer better, you'll have to learn to use the shell, read books and documentation and a lot of other things...but again, if you just want to use your computer for writing some documents, browsing the Internet, listening to mp3s and watching some DVDs etc. that's not strictly necessary. As for the installation, it's not too difficult either, but in this case you have to read the documentation and get to know what you're doing before starting. If you don't feel like doing it you can ask a friend to help you out or ask a computer expert who understands about GNU/Linux. Most computer hardware is supported by Debian GNU/Linux and during the installation it will be detected and configured properly, some hardware however is not supported or need further configuration, again if you don't want to spend time reading some documentation you'd better ask a friend about this.
Anyway, what I can tell you is that I'm not a computer expert but reading the documentation I was able to install and set up Debian properly on my computer and now have a dual-boot machine with Debian and Windows98. The only thing that I've been unable to set up is the modem, and that's because it's a winmodem, which means it's designed to work specifically with Windows OSes and therefore there's no easy way to get it working with GNU/Linux.
I really enjoy experimenting so I'm also learning to use the shell, text editors and so on. At the moment I'm using the enlightenment window manager, which is very fast (ideal for my old PC) and has a futuristic look. One of the great advantages of using GNU/Linux is that you have the possibility to experiment and to choose, for example there are at least more than 12 window managers from which you can choose, all with a different look and feel.
Of course there are better reasons to choose Debian GNU/Linux and free software in general, I could talk about them, but they've been laid out more clearly and extensively by other people, so to know about them, please refer to the GNU's website www.gnu.org in the philosophy section, this is the best and most accurate source of information about what "free software" is.