See, this is a new thing that apple started doing when they shifted to Intel C PeeYews. The earlier Motorola systems would and could run ANY MACOS from OS 7 to OSX 10.3.9, with Classic installed even.
But then after the first Intel iMacs were made, suddenly with 10.5.8 (the last MACOSX which was offered for PPC as well as Intel), they stopped supporting all of the people who had just bought 4,000 dollar G5 Dual Towers.
They should have kept developing the parallel OS's like they did with 10.5.8, with NO limitations on hardware.
It's the stupidest thing they ever did, imo.
And in fact this dumb decision cost them dearly, and when Microsoft released Windows 7, well, people were loading it up into MACS using Bootcamp.
"The best Windows Machine I've ever run is a Macbook Pro using Bootcamp" - I thought I had coined this phrase until I heard it coming back at me from all directions. and I think the reason for this, why Apple computers can run Windows OS's SO WELL, is they have a unified collection of device drivers, there is no nVidia vs ATI, Mostly they use ATI Radeons, and similar, with the connector for the Cinematic Display. I love that Cinematic Display, I wish I could make it run on my Windows machines, but I would have to rig a power supply
In general most Intel Macs, have similar chip-sets and Bluetooth and wifi, and I think that's why it runs so smooth, Apple should go into business developing Windows Device Drivers, they do it so well with their own proprietary hardware heh- I'll bet if they put the effort into making 3rd party device drivers, they wold kick arses.