Sometimes one's choice of a comparison gives subtle hints about hidden assumptions. A recent ZDNet article discussing Apple's and Microsoft's upcoming operating systems was probably driven by the fact that both OS vendors plan upgrades in the near future (one much sooner than the other). I've long thought that the real contenders in the consumer OS space have been Windows and Mac OS X. If meteors wiped Redmond, Washington off the face of the earth, my first alternative would be an OS from Cupertino.
That will, of course, cause Linux fans to froth at the mouth. How dare I suggest that Linux isn't a serious contender for desktop computers, and in particular, the wider group of non-technical computer users? It's pretty clear from the statistics, though, that most people who use desktop Linux are orders of magnitude more technical than the average computer user.
Compatibility and ease of use are the driving factors here, in varying degrees. Apple lacks compatibility with the majority of software available, but has high ease of use driven by levels of stability derived from Apple's control over the platform and great UI features. In Microsoft's case, the balance shifts toward compatibility. (Not to say that Windows is ugly, but the Mac OS X is damn sexy, IMO.)
Many want to make Linux a contender on the desktop. As I've argued previously, that's going to be hard because the people who contribute to Linux tend to be highly technical and less interested in the needs of non-technical users. Why am I wrong? And what features of Linux are most relevant to non-technical users?