With El Capitan, Apple continues the pattern it set first with the Leopard and Snow Leopard releases: That is, the naming convention signifies that the new version of OS X is more about refinements to its predecessor -- in this case, 2014's Yosemite -- than it is about new features. (El Capitan is named after the famous rock formation in Yosemite National Park.)
While El Capitan offers a slew of smart changes to Yosemite, it does offer a dash of useful new features, too. Here are the ones I'm looking forward to most.
Siri, is that you
Spotlight gets some needed enhancements and can finally be moved around the screen instead of being locked to the center of your main display. You can also now check on stocks, sports data (including schedules, standings and information on favorite athletes), as well as current weather conditions and forecasts. But that's not what makes the updated Spotlight so interesting.
By now, most Apple users know Siri's voice and what "she" does: Siri answers questions. But Siri is actually a collection of background services designed to respond and offer results based on natural language queries. In El Capitan, Spotlight now seems to be capable of doing much the same.
On stage at WWDC, Craig Federighi, Apple's senior vice president of software engineering, demoed a search for emails from Phil Schiller that Federighi had ignored. Spotlight quickly found the emails. The primary difference between using Siri on iOS devices and using Spotlight on the Mac is that the Spotlight commands are typed in. It looks like some of the software running Siri behind the scenes on mobile devices has been injected into El Capitan.
Apple engineers have also created a new API for use by developers that will allow non-Apple apps to display search results of in-app content. This will open the doors for better search results and is evidence of Apple's efforts to bring its personal assistant to the Mac. Given how often I use Siri and how much better it has become, this is a welcome step.
Managing windows and apps
Window management via Finder and Mission Control also gets some welcome improvements in El Capitan. Last year, Yosemite offered applications a full-screen toggle, finally giving the Green Finder button something useful to do. This year, El Capitan lets you double-up your full-screen apps in a split-screen view; this view is activated by dragging a Finder window to the top of the menu bar and then dropping that window on an existing full-screen app Space in Mission Control. (A divider separates the apps on screen, and both apps operate independently, even though they're sharing the same Space.)
A Mac has a single menu bar at the top of the display that dynamically changes based on the front-most app, and that behavior stays the same, even in the Split Screen view: The app being used takes over the menu, split screen or not. It's an elegant solution for simultaneous use of dual apps.
If you want, the divider can be dragged from side to side to change each app's real estate. This is especially useful for doing research in a browser while, for instance, writing about OS X, and it's something that is already available on Windows. (Apple's version is harder to trigger accidentally, however.)
Before, if you wanted to place an app or any Finder windows in their own virtual Space, you had to launch Mission Control first; now any window that's dragged to the menu bar activates Mission Control, allowing you to drag and drop to create a new Space in full-screen mode, or letting you drag and drop to choose a new or existing Space in which to drop the window. Essentially, Apple reduced the steps needed to perform a pretty common maneuver. If you're a fan of Spaces, you'll appreciate this.
Mail improvements
There's a common problem with full-screen app support in Yosemite, especially in apps like Mail: Sometimes you need more than one window open, and full-screen mode didn't allow for that. In Yosemite's full-screen mode, the compose window wouldn't let you back into other mailboxes -- or let you do anything in Mail -- until you finished composing your email. El Capitan fixes this behavior by allowing a compose window to be minimized, letting you back into the app without finishing the message first. And if you're composing more than one message, each one shows up in tabs, just like a browser window would in Safari.
Data detectors in Mail have also been improved, and now offer suggestions at the top of the email body upon finding phrases in a message that could lead to calendar entries, like "Let's go out for dinner at 5:00." Apple marketing calls this suggested events; the same feature is also available for potential contacts.
Finally, Mail offers swipe gesture support, similar to what you see on iPads and iPhones: Using the trackpad, you can swipe left or right in the email list to perform actions like mark as read/unread and delete. If you're accustomed to doing this on an iOS device, the move will come naturally and will help you sort your mail faster.
Safari gets pinned
Safari continues to evolve, and this year gets pinned sites and built-in AirPlay support for videos. (AirPlay allows you to wirelessly beam content to an Apple TV-connected television.) Pinned sites are simple: They're invoked by going to the Window dropdown menu and selecting "pin tab." After you do that, the page will stick to the left of the Tabs bar for quick access in all current and future Safari windows. As for the built-in AirPlay support, it may not be good enough to supplant ClicktoFlash -- that's a Safari extension that does much the same thing and even lets you download content -- but it'll be good enough for users who just want to stream video to Apple TV.
Perhaps the best feature in Safari is the way the browser will combat those annoying background tabs that auto-start video or audio. Safari lets you mute all sound from every tab within the Web address bar, and then goes one better by showing you which tab has the offending site and content. Smart.
A few more tidbits and tweaks
El Capitan is full of minor refinements that make the computer easier to use, but the one "advance" that is so drop-dead simple it could be considered brilliant involves something all of us do: When you lose your cursor, what do you do Shake the mouse, right In El Capitan, the mouse pointer responds to that by growing larger and more visible, making it easier to spot. It's the little things like this that can dramatically improve the user experience.
Another refinement that should make a big difference in overall performance is the addition of a technology that made its debut on iOS and is now making its way back to the Mac: Metal. A set of graphics APIs that take advantage of the CPU and GPU, Metal offers better performance than OpenGL. The built-in apps that come with El Capitan have already been rewritten to take advantage of Metal, but third-party apps need to be redone using the Metal APIs before you'll notice any difference. The result: Apple says graphics performance across the board is up to 50% faster while also being 40% more efficient.
There are other new features coming, of course, and all of them combine to offer iterative enhancements. After the major UI updates that arrived with Mavericks and Yosemite, taking a pause to polish OS X makes sense. Although it's not due out until the fall, you can sign up for access to public betas. (The first beta is expected next month.) And it's notable that El Capitan will work on the same hardware that runs Yosemite. So if you have an older system, you won't need to upgrade your hardware to get the new OS X.