Editor's note: This review has been updated from its original to include source information.

Among the news and announcements at the WWDC Keynote this morning, Apple previewed the next iteration of Mac OS X Leopard. Snow Leopard, as Mac OS X 10.6 is known, appears to pack a lot of new features and is slated for release in September, though no hard dates were announced during the Keynote.

The goal of Snow Leopard, according to Apple, was not to reinvent Mac OS X, but to refine, simplify, and speed up the overall experience. They were careful to point out Snow Leopard is not a complete OS replacement, but an expanded update to the current system. During the first public preview of the latest version of Mac OS X 10.6 this morning, we got to check out some of the changes Apple proposes will make the system faster and easier to use.

During the Keynote, Apple's Bertrand Serlet outlined a few of the major new features in Snow Leopard. For coverage of Safari 4 and QuickTime 10 features, read this blog post from Seth Rosenblatt.

In addition to QuickTime and Safari improvements, Serlet hit upon several planned enhancements to the latest Mac OS X. Apple claims they have managed to decrease the install time of the operating system by 45 percent. If this turns out to be the case, the OS will take up six fewer GB than before, which might mean a significant storage boost for current Leopard users. It's difficult to determine if this will be true for everyone--people run different configurations on several different Mac models, making it difficult to nail down exact numbers. Any decrease in system bloat is certainly a good thing if Apple can pull it off.

According to Apple, changes to Leopard are mostly small refinements that make it easier to use. We already liked the convenience of Expose to quickly find what we're working on when there are a lot of windows open on the desktop. But with Snow Leopard, an interface enhancement would let you click and hold on a Dock icon to bring up all the windows associated with the application. Apple also demonstrated the ability to drag an item from one program, use Dock access to Expose, and move files where you want them--like grabbing an image to send in an e-mail, for example. Usability refinements like these are small, but might make using a Mac a more seamless experience.

Snow Leopard
Long-awaited support for Microsoft Exchange makes it easy to create meetings, use global contacts, and more. (Credit: Apple, Inc.)

We were happy to see that Stacks is slated see an upgrade, including the ability to open and explore folders within the stacks window--the current version opened the Finder when a folder was clicked. The possibility of an added scrollbar to Stacks will be a very welcome addition. With the current version of Leopard, there is a limit to how many programs will fit in the Stacks window, forcing you to go to the finder if you don't see your program. During this part of the presentation, Serlet also showed how Snow Leopard will be able to preview images, videos, and PowerPoint presentations, even if you don't have PowerPoint installed on your Mac.

Support for Microsoft Exchange is a feature many users have been waiting for (for far too long), and with Mac OS X Snow Leopard, Exchange support may finally become available. During the demonstration, Apple showed how you will be able to add an account to Mail, choose Exchange, and your Mac will autodetect Exchange information from your address book, or you can enter the information manually. From there, Apple says you will be able to use Exchange's global list of addresses and drag and drop contacts into iCal to easily schedule meetings. They also demonstrated smart technology surrounding meeting locations enabling your Mac to discover time conflicts and change the meeting time and location to work for everyone. These features look great, but we wonder whether Apple plans will line up with reality when Snow Leopard is actually released.

With Snow Leopard, Apple claims they have made all of the Mac's core applications take advantage of the 64-bit architecture. This could mean faster applications, faster loading times, and smoother overall performance. Snow Leopard also should add support for most hardware with Open Computing Language (OpenCL), which would let any application tap into the GPU computing power previously available only to graphics applications. Apple says they have improved threading across multiple processors using what they call a grand central dispatch to control threads. These tweaks might help improve overall performance, but we'll have to wait for Snow Leopard's release before we can judge the efficiency and speed of these refinements.

With Snow Leopard being more of a service pack than a complete system upgrade, it seems Apple has priced it accordingly, letting current Leopard users pay $29 to upgrade. The family pack, which allows you to install the new OS on five computers in your home, will cost $49. Though Apple didn't announce a specific date for release, we already had some idea it would launch in September. Maybe the improvements will be enough for people to pay out of pocket for this patch-like upgrade.

Jason Parker has been at CNET for more than 13 years. He is the Senior Editor in charge iOS software and has become an expert reviewer of the software that runs on each new Apple device. He now spends most of his time covering Apple iOS releases and third-party apps.