Mac displays are not very good. Their color range is poor. It is the middle-top end of consumer displays, but it is by no means a professional display. I wouldn't even dream of doing anything requiring accurate colors on an Mac display. Their 30" is about as relevant as Xserve. It is not their target demographic any more.
I am not knocking Mac hardware. Their mobile hardware is the best on the market. However, the perception that Macs are design machines came from when Photoshop was a Mac exclusive. This has not been the case for a very long time and I would say the PC version of Photoshop is significantly better than the Mac version as it stands. I have a MacBook, but I also have a PC largely because I use Photoshop many hours each day and Photoshop on OS X is bad.
Color management, besides being supported by Windows, is more applicable to print design and pretty much irrelevant when it comes to design viewed on a screen.