An unintuitive interface that they have to relearn is usually the first put off. Sure you can learn it, but for all the claims of how easy it is, most people don't find this to be the case, and there are independent studies out there that prove this.
If Mac were better, they would be the number one brand. They would be running the business desktop, the business servers, etc.
Actually, I've seen studies that the MacOS actually is faster and more intuitive OS when it comes to workflow. And just because you have to re-learn a logic the OS uses, it doesn't mean it's a bad one - simply that you are used to some other system. It's just natural a different OS will feel weird at first. My MacOS experience has been very positive even though it was a tad strange at first, I came from a background of using different Windows versions for a decade before getting my first Mac. I wouldn't be a Mac guy if I didn't like it!
The sole fact that Apple is successful in selling computers to a market that's saturated with one system in monopoly position, even in a position where the people have to get accustomed to a "weird" OS and you can't even get every piece of software for it, does prove that Apple is doing something right with it's machines.
Most PC-nerds are happy to put this under "pretty covers and a lot of marketing", however if Mac would be just a company that does a poor machine with a poor OS, throwing a bit of glitter and marketing hype on top, people simply wouldn't buy it enough to keep the company up. We are living the information age, not the wild west where you can travel around selling snakeoil, word gets around.
And SuperDuck claiming that "Macs just won't make the cut.." - it's funny, my university's Comp. Sciences department has a few pretty hardcore Mac fanatic heads of staff - even to the point that the CSc dept has a couple of full-Mac classrooms, plus at least a couple of Macs available for student use in most computer halls around the whole campus. But hey, what do they know, they're just IT professors, right?
It's true though, that some fields can be very PC-oriented. If you have interests in those fields, it's obvious that you want to use a PC as a work machine (or simply dualboot your Mac to Windows), nothing wrong with that. But for more generic use, I still feel that Apple offers products that are superior to Windows boxes when it comes to the user experience.