First of all, I really liked that ad. It's the perfect antithesis to the outright smugness of Apple's ad campaign, which I really, really hated, despite being an avid Mac user.
Secondly, @ Keith - no, Apple still use the Intel x86 architecture in their machines. AFAIK Intel developed the Core 2 processors for Mac, but then went ahead and replaced the entire Pentium range with Core 2s anyway. The only difference between Macs and PCs is that Apple design and specify all their machines, meaning that because OSX and its applications only have to run on a narrow range of hardware, that they are far better optimised for running on that hardware.
Finally, @ Orwell - Yeah, getting OSX to run on a home-built PC is by no means an easy feat, and at least for a lot of the time, using hardware that falls outside of Apple's spec tends to completely break it, but there have been reports of users managing to assemble stable systems comparable in performance to the fastest 2x quad-core Xeon Mac Pros for around half the price you would pay if you bought from Apple!