I have a confession to make before I begin this review of OS X 10.8 Mountain Lion: I never really used or liked OS X Lion. Sure, I installed it on my iMac at home and played around with gestures on a Magic Trackpad, but my workhorse 15-inch MacBook Pro remained stubbornly on Snow Leopard, Apple’s previous version of OS X. Snow Leopard was in many ways the pinnacle of a previous era of computing: a fast, stable, reliable desktop operating system that bore no trace of influence from Apple’s enormously successful iOS products. Lion, by contrast, represented Apple’s first steps down a different path — the company literally said it was bringing iOS interface concepts like gestures and fullscreen apps “back to the Mac.” Some of the changes were drastic, some were minor, but in the end Lion never felt as tightly polished and cohesive as Snow Leopard. Worse, it sometimes felt a little slower too.

So although my preview of Mountain Lion in February held significant promise, I still approached the final build we were given to review with some hesitancy. If Lion was Apple’s first tentative step down the road towards a unification of iOS and OS X concepts, Mountain Lion is the company hitting full stride. Features like Notification Center, share sheets, and AirPlay mirroring are lifted almost directly from iOS, and iCloud support is built into the foundations of the system.

But there are also some important changes to OS X itself: the new Gatekeeper app-verification system is an attempt to blend the tight security of App Store apps with the traditional freedom of web distribution, and there are tons of tweaks to developer-level APIs to enable new functionality. Most importantly, Apple says Mountain Lion is both faster than Lion and significantly faster than Snow Leopard. It might share a name with Lion, but Mountain Lion is a whole new beast. And all of it is just $19.99, which is basically impulse-purchase territory.

But even still — is it worth it? Should you upgrade? Is the future of OS X really just hand-me-down iOS features, or is there more going on here? Read on for the full review.