For several years Apple has been releasing two operating systems: one for their mobile devices and one for their computers. While they are both fantastic systems, the problem was that people who used both systems had to make big changes when shifting between the two. Every summer Apple would release a new iOS version, which included fantastic new features. Every year or two Apple would unpredictably release a new version of OS X that had new features that were missing from iOS. These two systems played feature-leapfrog, with too much disparity between features. On Mac your reminders were managed within iCal and your notes were stored in Mail. On iPhone your reminders were managed in a Reminders app and your notes in a Notes app. Beginning with Mountain Lion, Apple is intending to keep the two systems in parity with each other, releasing updates at the same time and keeping the features in sync. Mountain Lion has Mail, Calendar, Reminders, and Notes, which all operate very similarly to their iOS counterparts. It has been implied that from now on, OS X and iOS will be on the same release cycle, with free or cheap upgrades available every summer.
Is it worth upgrading to Mountain Lion? If Apple again releases their upgrade for $29, it would be silly not to upgrade since Mountain Lion is largely a refinement of Lion and has enormous benefits to users who already have iOS devices. The only reason you might not want to make the step up from Lion would be if your computer can’t run it and a new computer isn’t in your budget. OS X Daily has a great list of what models support Mountain Lion, though be aware that this list is for the beta and it very well could change before Mountain Lion is released. Most Macs produced in the past four years or so should be compatible. If you have any questions about compatibility just email me your serial number and I can help you out.
If you want to read more you should check out Apple’s overview of Mountain Lion.