When I was in school for Graphic Design, of course the main labs used iMacs. They had just gotten some C2D iMacs to replace their old G4 setup. I've give Apple the credit for having nice displays with excellent color. Other than that, please lord give me a Windows Machine. The iMacs had the stock keyboard and mouse (which for home users could be replaced) but that mouse was a horror.

Much hate for single buttons (I'll take my highly customizable Logitech G5 or any of the older series I had). That trackball wheel was poor. Not only did it feel like I had a wart on my finger when using it, but it was very inaccurate. Zooming on a document was sometimes a pain. I'd barely touch it and I was maxed zoomed in. Try to zoom out with a good amount of touch and I'd go back 3 clicks.
And wow they had printer problems, though, I believed it was the printer/network themselves. That's a whole nother story.
Anyways, I was not in favor of the networking scheme they had setup for school. Granted, some files were large and you shouldn't save to your network drive directly. But occassionally when u did save directly to the network drive, the application would crash and you'd lose a save. So saving was always crucial..
Thankfull my profs where very kind and would let you go home during work time or sneak off to the video production lab that had Windows machines. Though they were slower and had CRT's, much nicer.
Years past, the benefits of the GD on Macs was there. But when I was in school, those benefits had all become myth and where still touted by some ill-informed souls and profs.
Why would I want to fork over Apple premium for hardware when I can build (or buy) my Windows machine for much less. And security? Please. Educate yourself in online safety. Don't be a moron. As the Apple 'fad' continues, you'll see more security issues pop up as they are targeted more.
Now for the interface, that's user preference I've found. But for what I do and for what apps are available, I'll stay with Windows thanks.