I use it because of the Freedom it provides.
I am not restricted by corporate agendas, greed, profiteering, and other such nonsense. Nobody is going to try to prevent me from transfering files or updating my programs or changing the media formats of movies I buy or anything like that.
I am not limited by obnoxious EULAs. I can copy it, hack it, give it away, customize it and do whatever I want with it. Give it to you, to mom, install it on multiple computers. Take a single copy and use it to run a entire school district or business.
It's 'mine', my computer is 'mine'. In a much more complete manner then is provided for by proprietary OSes. It's 'mine' on my terms, and it follows my own whims. If I don't like something I can change it, swap out peices or do whatever.
Do people remember hearing people freaking out on Microsoft and friends saying things like 'I bought he software, it's mine, why can't I install it on many computers or make many copies of it. I paid for it!'.
Nowadays people don't think twice about having to purchase multiple copies of software. It's 'normal'. People often think a person holding a position like was stated just above is ignorant or even selfish. Maybe even criminal if they end up carrying out their desires.
Personally I still feel that way. So to avoid the whole stupid mess and restrictions and other irritating things I simply refuse to use windows or os x for anything remotely important.
I don't have to pay extra for 'SDK's. I don't have to belong to any development club or subscribe to any special privilaged position to get cheap hardware. I don't have to sign away my rights in order to examine how programs work. I have access to the same tools and code that was used to build my OS in the first place. I have many choices between desktop environments, editors, distributions, and other such things.
Basicly all the perks and such that I can enjoy because the freedom that is afforded me by the generous programmers who made my operating system and applications.
I am more comfortable with Linux then Windows. It's easier for me to use and I only buy hardware and use software that is compatable with it.
Why on earth would I want to use Windows for anything? The joy of paying 75-400 dollars (depending on what functionality I want unlocked) for a single copy of a OS? With which I will still be called a pirate if I try to install it on both my machines at home. Applications cost extra, no proper way to upgrade the entire OS other then the core elements. Bizzare things like
this
Microsoft is a company that will sell controls to it's own customer's PC to other corporations (RIAA, Hollywood, pornographers, etc), that the customers themselves don't have, in the name of drm protections.. and then tell me that they are doing it because it's what I and other customers want?
It's almost otherworldly.
If other people like it, then that's fine by me. It isn't going to bother me even if it's a bit confusing. They have different requirements and different values. So that's how it goes. If Microsoft wants to impose obnoxious requirements with it's EULA, then that's fine. They can do what they want; it's their software.