John Siracusa writing for Ars Technica:

Mountain Lion is not the Mac OS of the past, but it also sets a course to a destination that is quite distinct from iOS. Despite the oft-cited prediction that the Mac will eventually be subsumed by iOS, that’s not what’s happening here. Apple is determined to bring the benefits of iOS to the Mac, but it’s equally determined to do so in a way that preserves the strengths of the Mac platform.

…

Apple’s online platform is the unifying force in its product line, not any one OS. Think of Mountain Lion as the best desktop iCloud client Apple knows how to make.

Over the past decade, Mac users made it through the most dramatic, unlikely, and successful operating system transition in the history of the industry. Last year, I noted that despite its king-of-the-jungle name, Lion was not the endpoint of a decade of Mac OS X development; it was the start of a new journey. Mountain Lion makes the eventual destination a bit more clear. Just hold on, my fellow Mac devotees, and we’ll make it there together.

The review is 24 pages long and covers most things that Apple’s marketing pages fail to mention. If you’re a developer or a power user, this will interest you.