This paper is a good read as we near
Mac OS X 10.2. Possibly one of the most underappreciated engineering feats has been
combining the single-user focused Mac OS and multi-user Unix environments. It's also an interesting reminder of the very different design goals, and the sort of feats and concessions that were made to bring the Mac OS out at a [relatively] affordable level.
A couple of paragraphs could probably be used to explain the problems facing the myth of
Desktop Linux:
This makes for an interesting system architecture. The ideal result is a system that can be the sort of reliable server platform we use today to host high-volume web sites, file services, network gateways, and engineering computation services while also being the simple to use home computer platform of choice. This is a daunting task, because the server platform goals mandate a certain level of complexity (high security, performance tuning parameters, various network servers, etc.), while for most home users, simplicity overrides other concerns.
Unix and Mac OS have evolved independently of each other, and there are fundamental assumptions made in one system which cause numerous failures in the other. The capabilities of the available file systems, the networking protocols, and the user/system model are profoundly varied, often in ways which cannot be rectified without changing the architecture of system components. Additionally, people use the systems in very different ways and expect different behavior from them.
Other issues such as file system layout, packaging, and so forth are also discussed in the paper.