Among otherwise valid points about the ease of porting Unix applications amongst Unices, Dan Benjamin slips on what is, IMHO, a common mistake about Apple (his emphasis):
Apple is a hardware company, not a software company, as evidenced by the real way that Steve Jobs saved Apple: Powerbooks, iBooks, and the iPod.
The initial Mac was not just a computer. It shipped with a set of software, by Apple, that made a huge difference at the time. I'm lucky (or may be not) enough to remember MacWrite, MacPaint and MacDraw. When Jobs took over Apple again, the company software was non existent (if you except the spin-offs FileMaker and Claris) and the hardware line was a mess, no logic between models and, most importantly, absolutely no entry level computer. His way to save Apple was to simplify the product line and, obviously, to reintroduce an entry model: the iMac. This was simple and doable, for a company in bad shape, both financially and spiritually, that couldn't do everything at once.
In the past years, Apple has rediscovered its true nature: it is not, dare I say, just a hardware company. It's a platform company. It excels at designing products, be they hardware or software or service, provided it can design the whole experience.
As for the claim that Apple is not a software company, I oppose: QuickTime, Safari, iLife (iMovie, iPhoto, iDVD, iTunes and GarageBand), iSynch, iCal, Final Cut Pro (which it bought from Macromedia but greatly improved) and Express, etc. without forgetting Mac OS of course.
Apple is always at its best when it remembers that it isn't just a hardware company.