Mark Shuttleworth, a noted personality in the Linux world, has been much quoted lately for comments he made at OSCON regarding the OS X desktop and the need for Linux to exceed its usability. While those comments have merit, it is to Linux's credit and advantage that it has focused more on the foundation of the OS than its GUI interfaces.
Throughout their histories both Apple and Microsoft have concerned themselves more with presentation than substance. While that has helped them win market share on the desktop, it has left their products riddled with security holes.
While few seem foolish enough to defend Microsoft products' security, Apple aficionados often claim a superiority the facts cannot sustain. Independent security surveys of the OS X code commonly find that Apple's coding practices introduce great numbers of vulnerabilities into the underlying OpenBSD code. To Microsoft's credit, they are far less dismissive of their failings than Apple.
Linux, on the other hand, like Unix before it, has been more concerned with the strengths of its foundations and has evolved its user interfaces in this light, rather than despite it. Those who assert that Linux and Unix aren't intrinsically more secure than Windows just don't understand the effect such a fundamental difference in philosophies produces.
While I applaud Shuttleworth's goal of producing an improved desktop user interface, the Mac paradigm is not one I'd care to see embraced. In all too many respects the saccharine Mac UI purposely isolates the user from the chance to understand what is going on with their machine and its software. The attempt is to produce addiction, more than provide real ease of use, and it is often effective. Ultimately, however, to use a tool without understanding its function is to invite accidents. In that respect, Steve Jobs is more Pied Piper than emancipator.