One of the things I’ve always appreciated about Apple is how they approach upgrades. While companies like Microsoft sell their operating systems at an exorbitant licensing cost, Apple has favored an approach in which they release their operating system upgrades either for free (as with iOS) or at a low cost that anyone can afford.
The benefits are big. Updated versions of operating systems tend to be more secure, which helps guarantee OS X’s lead over Windows when it comes to malware. Naturally, then, Mac users tend to adopt new versions of OS X faster than Windows users upgrade, but the statistical disparity might surprise you.