Today, there’s only one operating system: Unix. (Okay, there are two, but we’ll get to that.) This is why I contend that the OS doesn’t matter—or that we need to take another look at the word’s content, at what we mean when we say ‘Operating System’.
Jean-Louis Gassée stating the obvious. But he is right. A good read.
The only exception is Windows. Initially built on top of DOS, Microsoft painstakingly added version after version, always striving for backward compatibility while, at the same time, adding new features. It didn’t always work well (who wants to remember Windows Me and Vista?) but it worked well enough because Microsoft never gave up. They fixed mistakes that they claimed didn’t exist, and now we have the well-respected Windows 7. (Inevitably, critics will say that Microsoft wouldn’t have gotten away with such a tortuous path if it weren’t for its vigorously enforced monopoly.)
Unrelated : It’s interesting (read: irritating) to me that Microsoft are also the only Smart Phone manufacturer who are going with their own proprietary Graphics API.