"In short, the more I use Mountain Lion, the more I feel like 10.7 and 10.8 should have shipped as one operating system update, not two.
Is Mountain Lion worth upgrading to? Yes. It modernizes OS X in many areas, and makes working with iOS devices easier than ever. But at the end of the day, 10.8 is the realization of the goals Apple set with 10.7, and it shouldn’t take $19 to make Lion worthwhile."