Go sit in any college lecture hall and you will see at least 60% Apple products. Apple heavily markets toward college students (Student discounts and back to school promotions) and these same students will be buying Macs for their homes and offices soon.
OSes have grown much closer to each other over the last five to eight years; websites (or "the cloud" or whatever term you wish to refer to server-browser-driven software) are much more important; the relative cost gap between Macs and Windows machines is much smaller; Apple laptops appear to be vastly better made than any mainstream Windows laptops save Thinkpads.
Take these together, and you'll see a lot of Aluminum MacBooks on campus. Geeks like them because of the Terminal, GNU toolchain, and the fact that other geeks have spent lots of time optimizing the general OS X programming environment; everyone else likes them because they're more aesthetically attractive than Windows laptops.
I agree that the obstacles to entry are much lower for Apple now. But there is still a significant price premium for Apple laptops. Maybe it's not consequential for people that can afford to pay tuition in a Western university but for the rest of the world that premium is still decisive.
Which is exactly why competing tablets haven't gained ground. Why buy a less usable device for the same price? Things in the tablet market will only get interesting when and if Android vendors can significantly undercut Apple.
But now that students are taking on more loans so they can afford it. Now, Apple doesn't have to entice you with a 40% discount. They know you'll buy it anyway so 10% off is more than enough for them.
Depends on the college. I sat in on a CS class recently at a local university and there were 2 or 3 Apple products in a lecture hall of 100 something students.
