Mac OS X Beginnings: Cheetah (2001)

From http://web.archive.org and Wikipedia

Finally complete and fleshed-out, and taking suggestions by developers and users, Apple modified and implemented it's first official 10.0 OS release, codenamed "Cheetah" (the big-cat naming system for subsequent releases continues today). Cheetah was the culmination and refinement of brand new ideas—not just an overhaul an older OS—combining a Unix-like Darwin kernel (Google it) with features from NeXTSTEP and specific design elements from OS 9 (like, say, the Finder).

The Cheetah release gave Apple fanatics a new reason to love their computers. Re-invigorated after suffering through the 90s dark ages, Apple and its avid users got a glimpse at the light at the end of the the tunnel.

Release: Mac OS X 10.0 "Cheetah"

Features: first official stable release, completely different codebase from OS 9, new user interface, improved networking, added support for AirPort wireless technology, full PDF support and the ability to create PDFs from any application, the fully-feature Mail application, other essential apps like Address Book and TextEdit, and the Apple logo moved back to the upper left of the menubar.

Drawbacks: A newly-minted OS, the system still had many bugs to be squashed, the interface was criticized for being too slow, and there were a few key features missing like CD burning and DVD playback, which were both available in OS 9.

Price: $129 ($100 for an upgrade from public beta)