People who adopt Macs know its going to be different. The guy in the shop is often saying how much the same it is, and the user doesn't realize that it is different until they try and put the printer driver disk in and it doesn't work.
First, they have a positive reinforcement: Mac is "hip", so you'll look cool by using their products (the fact that everybody and their mother owns one or ten doesn't seem to diminish this perception), and also a negative reinforcement because everybody knows "Apple makes easy-to-use products" so if you don't learn to use them quickly you'll look bad.
I'm sure Linux and *BSD have earned more followers by looking different or difficult than by trying to be "easy" (whatever that word means). But that's a discussion for another day...
Not thus far, but once there is a viable "underground" replacement suddenly the Apple will become passe and everyone will be on to the Pear. Apple is nearing that tipping point, at least in some markets. Once trends get big enough, they stagnate until something comes along and replaces them; Apple is approaching stagnation. The market is ready for real disruption if someone can put the pieces together correctly.