I think that Macs elicit a fierce loyalty in a certain subset of users, i.e., some folks passionately love Macs. I think that the majority of users could care less and see Windows and Macs as essentially equivalent, but use Windows since its more common and profits from the higher amount of money invested in it. There are very few who are passionate about Windows.
IMHO, the secret of the Mac was control over everything, which was good for technology but was a flawed business model. The very thing that makes the Mac a Mac is what prevents it from ever being as big as Windows. For me, Windows is essential since the (non-graphics) software I use is not available for Macs or is lagging behind. When I do use Photoshop like stuff, it's perfectly adequate for my purposes. The big question we face at my college is if the Mac is that much better in some applications to justify supporting two platforms. If we decide "no", then it really won't matter what graphics artists elsewhere use; ours will use Windows.
