PCIe cards. Multiple matte 30" monitors. Anything really CPU intensive.

I think he meant, why wouldn't a windows/unix/linux machine with similar hardware work just as well?

Because it doesn't run OS X?

Most creative pro apps are only available on Windows or OSX. I don't hate Windows7 but I find OSX superior (integration, stability, decent shell etc). If you want OSX, you generally need a Mac.

I'd switch to Linux if the apps were there, but it's not even close. And I'm an edge case, I suspect most creative types would rather not mess with xorg.conf.

That's why I wish, over and over, for a Wine equivalent that runs OSX apps.

I have ran some windows audio applications on Ubuntu 10.04 and the timing accuracy (tested by specialist software) was several orders of magnitude higher. In addition, I can achieve higher workloads. This is all with software that wasn't even compiled for my OS.

Logic Pro with high numbers of tracks and effects/filters.

Anything that needs workstation-level graphics like the NVIDIA Quadro (for doing stereoscopic graphics, multi device synchronization, broadcast pipelines, and more).

IOS + OSX developers (edited out my not really interesting comment about XCode)

Final Cut Pro?