When I was new to Linux, I thought, "what's so good about it" too. So, I tried it out - and I liked it. Besides the reasons everybody else gave why Linux distributions are good (although I just skimmed over), I like it because: - Software repositories - just open a terminal, or a GUI frontend if you prefer, and search for basically whatever you want, and get it. Whether you're using a terminal or a GUI frontend, it tends to be much easier to install a bunch of software at the same time than with Windows (really, what's easier, checking a bunch of checkboxes of software to select the software you want - and know is safe, and if it weren't, it wouldn't really matter anyway because Linux is pretty virus-proof - and then clicking "Apply", or searching around Google for each program you want, risking viruses and spyware and having to tediously go through each installer?). Depending on the distribution, the package manager can handle dependencies too, which is another less thing to worry about - if a program on Windows depends on something, the library will often be included with the program, which wastes hard drive space if multiple programs use the library and makes the library harder to upgrade, or you'll have to download it yourself. Upgrading on Linux also tends to be much easier, as applications in the repositories have a standard upgrade procedure which lets you easily choose what you do and don't want to upgrade, without having to go through twenty separate "UPGRADE ME!" boxes on Windows. - Customizability - distributions of Linux, besides each being different themselves (like Gentoo being well-suited for experienced users who want to control nearly every aspect of their software and make it completely optimal for their systems, and Ubuntu being simpler and much more intuitive), and be further customized to practically whatever you want. With a bunch of window managers and desktop environments to choose from - which are customizable themselves - and a variety of applications to tweak your desktop to your liking, it just totally beats Windows. I do think the Windows Vista and Windows XP themes are decent, and there are some programs to customize them, but Linux distributions are still much better at letting you not only customize the way things look, but the way things work. - Programming - I love programming on Linux. Windows is decent for programming too, particularly if you're using .NET, which is also by Microsoft, but Linux has so many free useful tools to help you develop your software (ranging from complex integrated development environments like KDevelop to command-line tools like grep to search for/in files or text and ffmpeg to convert practically any audio or video format to another). There are a few downsides to Linux, but it's often due to things being proprietary (meaning that it isn't really the fault of Linux distributions); for example, it tends to be harder to use proprietary file formats like WMV and proprietary hardware like Nvidia graphics cards. And there are certain popular programs for Windows (that are usually proprietary, so people couldn't even try to modify the source to make it work on Linux if they wanted to) that don't won't on LInux, but many will work with WINE, Cedega, and CrossOver Linux.
