The Snow Leopard cometh. After a modest demonstration alongside a hopped-up iPhone and slightly revamped MacBook at this year's Worldwide Developers Conference, the long-awaited update to OS X finally gets its time to shine on August 28. While Apple has shied away from painting the new Mac operating system (OS) as a landmark release - even the name implies that it's just a revision - Snow Leopard will bring with it a slew of upgrades that Apple fans have long awaited, and many that should pave a path to unlock even more performance as developers learn to fully take advantage of them. But with so many features that run more than just skin deep, Snow Leopard isn't an easy beast to understand. We sat down with senior Macworld editor Rob Griffiths to better explain what's in store, what could change for the worse, and whether or not most existing OS X users will want to upgrade.