But there were past times, darker times, in the history of OS X—we didn't always have widgets, Expose, or that rock-solid stability Apple pimps so hard as it blasts that card castle, Windows. Let's take a trip in the OS X Time Machine (not that one) and reminisce over former feline days of yore.
OS 10.0 "Cheetah" Released March 24, 2001, the first consumer version of OS X left the Classic Mac OS in the dust—though much like Rosetta eased the transition to Intel processors, the Classic environment allowed you to still run older Mac apps. Cheetah introduced the Aqua interface, the Dock, and Mail. But it was also unstable, sluggish (blasphemy in the current Apple canon), and hardware didn't "just work." Put another way: It was bad enough 10.1 was released as a free upgrade less than 8 months later.
OS 10.1 "Puma" Puma was essentially a glorified service pack designed to fix Cheetah's problems, so most of the improvements were under the hood—better performance and hardware compatibility, but not much in the way of actual new features.
OS 10.2 "Jaguar" Performance was boosted still further, but there remained some noticeable interface lag on occasion. Features-wise, the slickly designed iChat client made its entrance and Finder snuck into every window. The cat system of code names also became part of the official OS marketing.
OS 10.3 "Panther" Launched Oct. 24, 2003, the OS X Mac users know and love today really took shape with Panther—Expose exposed itself for the first time and Finder was juiced up with real time searching and the now-familiar brushed metal interface. Panther also marked the shift to Safari as the OS's default browser.
OS 10.4 "Tiger" The state of the union. Intel processor support, Rosetta for PowerPC apps, Dashboard, Spotlight, and a more unified UI among a plethora of other updates—both to apps and under the hood—make up the Tiger package. Let's not forget Boot Camp, either. While not part of the initial OS release, it's definitely worthy of a nod.
And that more or less brings us up to speed—will Apple rewrite the OS X history books? Evolution or revolution? Stay tuned.
WWDC 07 [Gizmodo]