I've done it and it's not worth the hassle. It breaks every time there's an Apple update (which is very very frequently), doesn't give you Quartz Extreme (part of what makes OS X so efficient) and you'll have serious issues getting drivers.
RE Macs being PCs under the skin, completely not true. Macs have an EFI instead of a BIOS, they manage their power completely differently, they manage graphics and sound completely differently (in terms of how it's actually configured from a hardware point of view) and Apple really makes more of the hardware themselves than any other company out there.