It's no secret Apple's OS X has some security problems and Apple doesn't talk about them much at all. This Security Focus article at The Register points out some of the problems. SANS has listed OS X as a vulnerability in itself, which is probably over-reacting.
What came through loud and clear to me is that no one can feel safe just because of the operating system they use any more. Configuration is more important than choice of OS. Really. And running applications without vulnerabilities.