So by my highly scientific accounting, Mountain Lion costs $20 but nets $46.90 worth of enhancements. And that’s not even counting the other 170 features: the Preview app (now lets you fill in checkboxes and blanks in PDF forms), Gatekeeper (blocks evil software), new screen saver slide shows, the unified address bar/search bar in Safari, the scroll bars that fatten up as your cursor approaches, and so on.
Over all, then, Mountain Lion is a gentle, thoughtful upgrade. All 200 new features? No, not really. But 10 that you’ll use every day? For $20?
Yes.