(A companion page to why you might want to use Linux.)
Firstly, there's the obvious reasons why I use it:
I like to use computers, and I like them to do what I want to do. It's reliable, predictable, and does what it's told.
I use several computers, and buying Windows several times over would cost too much. Linux is free (or cheap), and now my running costs only extend to the hardware I buy, and the electricity it uses.
Linux comes with the servers I want to experiment with. Indeed many of them were designed for Unix-like systems, and Windows needed specially converted versions of the same software to do the same thing.
It also comes with applications for all the things that I want, and need, to do. They're free, dependable, and free of advertising and spyware.
All my software, operating system and applications, get updated with one updating and software installing system. Unlike Windows, I don't have to separately find updates for everything, I don't have to babysit updates, I don't have to reboot, and I can even update software that I'm in the middle of using.
I'm tired of the amateurish mess that Windows is, and has been over the last decade, while demanding the price of a professional product. They've no excuse for it, considering the money they make, and the staff they have available to them. I'm thoroughly sick of how much of my time it wastes. I've got better things to do, and work that needs to be done.
Freedom! My computer is mine again. I'm not owned by the software company, neither is my data.
I can get Linux for zero cost (operating system, and software), I can also pay for some versions, but the choice is mine to do it either way, legally.
The obligations on me, as a user, are zero. There is no user license that I have to agree to.
There are some obligations on those who want to redistribute the software, but nothing onerous. In most cases I can give away an identical copy, but any modified copies may need to be done according to some conditions. And there are some obligations on those that use some software to create other software, based on someone else's work. But that's another issue, not applicable to most users, and it's not unique to Linux systems.
Information on how it works is freely available. I don't have to make guesses, I can do things to fit in correctly with the operating principles. And I can change how it works, based on facts about how it works.
I feel free to trust it. I haven't had to fight against it, I haven't caught it doing things I find dispicable.
I can get plenty of useful advice and assistance, freely. I've even been able to report faults, and software updates have been released that fixed it the next day.
With the exception of two computers that came with Windows, as a package deal, the rest of my computer network is all Linux. Those computers are dual-boot, so I can still use what I paid for, but they're rarely ever booted into Windows. I do all of my personal and business work using Linux. I can type, print, e-mail, chat, publish, doodle, manipulate images, and so on, with it. For me, it does it just as well, if not better. I don't have to have the same software as the next person to be able to interact with them.
Which Linux do I use? Currently, it's Fedora. I started out using Red Hat Linux, moved over to Fedora, and I've had a dabble with Deli Linux, Mandrake, Ubuntu, and CentOS. I've also had a dabble with a real Unix, one of the BSDs. But I've stuck with the Red Hat based distributions because I'm more familiar with them.