The Mac works. That's a good reason. Let's just connect two displays to a Mac, color calibration works on both. Simple as that. On the PC it's a mess. As far as I understand it may work and there are better and worse solutions.
I have used Windows for many years and still use it at work, I'm a software engineer by profession with about 28 years of experience of computer using different operating systems, so I'm not computer illiterate I guess.
I have no experience with either Vista or Mac OS-X.5, I'm still on XP and Tiger. At home, for my photographic work I switched to Mac and never looked back. I would guess is that is what we see in the business, people are OS agnostic but they try Mac OS X and send the PC to pasture.
There are benefits to having a single vendor. Apple can select components that work together and support them from the operating system. On a PC you can switch everything, which of course gives freedom, but the price is that you need to install drivers for all hardware you add. There is much less guarantee on the PC that things work well together, that's the price of freedom.
To be more specific I can give a simple example:
I bought the ColorMunki from X-rite, run the installation script and that was that. I plugged in an external monitor into my iMac and now the calibration dialog pops up on both. I need to physically move the Color Munki between the screens, but that's it. To install the Color Munki on the XP I needed to download new version of the code, install another version of .Net. I think installation took about two hours. Now I have a problem with the PC it's used for multimedia so it is connected to an LCD TV and a projector. They need different calibrations.
What needs to be done is that you would download "Microsoft Color Control Panel Applet for Windows XP", and install it. In order of installing it you need to install another version of .Net and maybe other programs. So you spend another couple of hours in front of the computer. To add insult to injury Microsoft Color Control Panel Applet for Windows XP is a piece of crap, at least if intended as a gamut loader. The idea is that you generate a profile and change name on it, then with Microsoft Color Control Panel Applet for Windows XP you can install, make it default and apply it. Problem is that it's messy, undocumented and you are never sure what you get.
I finished up calibrating the projector, and adjusting the LCD TV using it's controls to look decent.
Now, why do I have a PC as a multimedia machine? There are some good reasons. I can add different cards, multiple hard disks and it's much cheaper. I could use Linux, which was my favorite OS until the need of color calibration forced med to switch to Windows. Setting it up was a painful experience, though. Installing Windows was not really easy, than I needed to upgrade BIOS, even if I only had the computer for a couple of days. Video was boggling down CPU and was hacky. After some research I found out that my Graphics Card vendor (ATI) had new drivers downloaded another 30-40 MByte from the internet and finally got it working. Most applications and especially video still ignore color management and installed color profiles, so getting colors right is still not easy.
Now I feel it's perfectly OK for any people to use any OS of their choice, but my personal experience with Windows is bad. May be that Vista is a great improvement but I won't any longer touch any product from Microsoft voluntarily any more.
So can anyone tell me now why one should choose Mac over Windows machines for professional photography? Vista is 64 bit, so is CS4, Mac is not. New Macbooks no longer offer FW 400, and only glossy screens, not to mention that if you want to run mac, you have one choice of manufacturer for the machine you run it on, not my idea of a great structure for the professional. I have been digital for 2 years, earning my living with location people photography in the advertising and editorial markets for 20 years. I shoot with both Canon 1DS2 M3 and PHase one P45+ (processed as 16bit) and never have a problem with file size, color compatability, workflow or processing speed. My custom laptop usually outperforms the Macs that my freelance digi-techs use. The only drawback to windows that I see is the otherwise computer illiterate professional art directors, art buyers and designers with whom I work who are still worried that somehow they won't be able to use my files because they were "windows generated". About once or twice a year I will hear from a designer or AD that the images I provided were off in color, only to find that they are not viewing the images on a calibrated monitor, once the images go into a production machine they say "Oh, nevermind". I guess that I don't really think I need to conform to a once necessary standard due to outdated conventional wisdom. Am i missing something? The cool looking cases or clever TV advertising? Guess I never worried enough about being cool or trendy. I am about due to upgrade some hardware though, so I'd honestly like to know, I've asked several of the folks I work with on a regular basis, and stil no decent answer except the preference to the Mac OS and perceptions that I've mentioned above.