I am a Mac user with no plans to switch, though I use Windows regularly as a secondary OS at work.
As much of a techie as I am, I like to do things with my computers, not do things to them. In other words, I hate doing system administration, and Windows demands way too much such handholding to keep running smoothly. ("Just run msconfig" someone said above. OK. But my Mac requires none of that, it just keeps working well on its own.)
I suffered through 3.5 years of Windows at my last job. I liked a lot of the design of the Windows 7 UI, but there are lots of little user interface details that are wrong -- especially in third-party software Microsoft has no control over. On the Mac, even third-party software tends to be consistent, which results in a lower cognitive load when using new software or switching between apps. (At that job, I had to use a specialized text editor on Windows that had really weird text selection behavior -- different from Word or Mac. It drove me nuts because I always had to remember "Oh, I'm in Program X, I can't use the same keyboard shortcuts and mouse gestures that work EVERYWHERE ELSE.)
Moreover, in those 3.5 years, I ran into problem after problem. I'm not a professional Windows sysadmin and I don't want to be. I never did figure out the causes of all the problems (some I did, but not all). I would have really liked Windows 7, had it functioned as designed. But whatever the reasons, it didn't work right -- I had problems nobody else in the office had -- and that ruined the experience. I have little doubt that a gifted Windows sysadmin could have fixed some or all of those problems, but I didn't have such a person available.
And this is coming from someone who is damned good with computers. A casual user like my mom would be hopelessly lost with those Windows issues and would either resign herself to accepting that "computers just don't work" or to paying someone to come fix it all the time. Her Mac just works, and her friends think she's this computer genius because of the things she does with it.
Someone said early in this thread that (s)he uses Windows and Linux and that the Mac is "unintuitive". Well, yeah, if you approach it as Windows (or Linux, which tends to clone Windows more than Mac). Intuitiveness means "work how I expect", so if you expect Windows behavior and it behaves like a Mac, you'll find it "hard", because the Mac isn't Windows and will not behave like it. The reverse is equally true. Malfunctions aside, neither one is really much easier than the other, but you will always find your "home" platform to be easier than another.
As for cost: Macs cost the same as comparable non-homemade PCs, by which I mean not only specs but also quality. That, for me, pretty much narrows things down to Lenovo's business products (which I think are fantastic hardware). When I bought my Mac Pro (tower, not notebook) in 2008, it cost $1000 less than a lesser-configured Dell Precision Xeon workstation. And now, 5 years later, that Mac Pro still works, has similar benchmark scores to this year's top-of-the-line i7 iMac (except I've enjoyed that performance for 5 years already!), and still has a residual value of $1500. That works out to an annual amortization of about $500/yr. (Not including the regular hard drive upgrades to house my ever-growing TV collection.) That's fantastic long-term value, even if the upfront price was high.
What Apple doesn't do is make entry-level hardware. It begins at midrange and goes up from there.
For me, Linux's achilles heel (as far as mass-market adoption) is usability. In particular, one of the core tenets of good usability is consistency, both within apps and between them. The Apple developer tools and, above all, developer culture strongly encourage consistency. The Windows tools and culture, significantly less so. And on Linux, not at all -- there is no central body with any kind of authority to create, never mind enforce*, UX guidelines. I don't think that a high level of consistency is compatible with the distributed development model of OSS. This isn't intended as an attack, just an observation of an unavoidable consequence of OSS.
*(Microsoft enforces incredibly strict guidelines for the Ribbon. If you want to use it -- it's patented -- you have to sign a license agreement that requires you to adhere to 200 pages of design rules.)
When all is said and done, though, I think it's petty to try and proclaim one winning platform. They each have different strengths and weaknesses which emerged because of the radically different goals and values of their creators and the circumstances under which they evolved. It means that there's a good system for everyone, and that no system is right for everyone. Pick the one you like best and move on -- and let me enjoy the system that works right for me without picking on me for it.
