Just like the last few versions of Apple's laptop-and-desktop operating system, OS X Mountain Lion ($19.99) came out of the gate this morning as the best consumer operating system there is.

At first glance, Mountain Lion looks like an identical twin of its predecessor, OS X Lion. Upgraders from Lion will face an almost flat learning curve, because almost every feature they've learned to use works in almost exactly the same way as before. But Mountain Lion unobtrusively slots in dozens of new features—Apple counts two hundred of them—that enhance sharing, messaging, cloud-based synchronization, security, Web browsing, instant notifications, and accessibility.

When installed on the latest Mac hardware—recent models and the new with Retina display—Mountain Lion even keeps working while the computer sleeps, downloading software updates, messages, mail, and much else while the laptop's lid is closed and its lights are off, so the system is up-to-date the moment it wakes up. Mountain Lion isn't perfect, but it leaves the consumer competition so far behind that you'll need to look hard for convincing reasons to use anything else.

While adding security and sharing features that make it a more powerful system for getting work done, Mountain Lion also makes some convincing advances on Windows' throne as the leading platform for playing games. The new OS makes it easy to use a Mac as a high-powered game console and media center, easily sending its screen to an HDTV connected to an Apple TV add-on box. Though Apple won't say a word about it, this "AirPlay Mirroring" feature clearly looks forward to a future TV manufactured by Apple itself.

Apple charges $19.99 to download Mountain Lion from the App Store and—for that single one-time payment—you can upgrade all your existing Macs from OS X Snow Leopard or OS X Lion. If you recently bought Mac—on or after June 11, that is—don't kick yourself: your upgrade is free. Don't bother trying to buy Mountain Lion on a disk; it only comes on a new Mac or via the App Store. If you buy a MacBook Pro with Retina display with Mountain Lion installed, be warned: you may spend so much time feasting your eyes on Mountain Lion's high-resolution desktop backgrounds that you won't get any work done. I only stopped being distracted by the gorgeous imagery when I changed my desktop background to a solid color.

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A Different Approach

Compared with last year's debut of OS X Lion, what's different is that, this time, 's release is imminent (it's currently available as a Release Preview). While Mountain Lion wins as a consumer OS, it will also be extremely interesting to see just how much attention it gets from businesses, too—especially smaller businesses that wouldn't take advantage of the Windows Server 2012.

Microsoft chose to merge a desktop OS and a tablet OS in way that seems likely to encounter serious resistance among their more conservative desktop users, to say the least. We'll reserve judgment on the success or failure of that integration until final code is released, however. In contrast, Apple took the best parts of its iOS phone-and-tablet operating system and built matching features into OS X, without delivering major disruptions to longtime users of either.

Simple, single-purpose apps like Mountain Lion's new Messages app are good examples of what's right in the OS X/iOS integration. The app exchanges messages with any iOS devices in an interface that matches the iMessage app in iOS. A complex app like the Safari browser keeps all its advanced features while adding a new "tab view" that, somewhat like Safari does in iOS, displays reduced side-by-side images of all your open Web pages and lets you switch through them with an easy trackpad swipe. The OS X Mail app used to be a catch-all that also stored notes and reminders, but now OS X has separate Notes and Reminders apps that match the ones in iOS—including location-based reminders that trigger when you enter or exit a specified address—and sync their contents with your iOS devices via the cloud. The voice-activated Siri system in iOS doesn't exist in OS X, but Mountain Lion includes a built-in dictation system that lets you speak text into any existing application; I've got more to say about it below.

Mountain Lion feels like the fine-tuned product of years of careful thinking about how an operating system should combine innovation and consistency, while Windows 8 feels (so far) like a 1.0 release: big ideas, paradigm shifts, and a lot of work still to be done. (For a glimpse of some of our Windows 8 issues, read our . It wasn't pretty.) Swipes, squeezes, and other gestures that work on an iOS device will also work on the trackpad on an OS X machine, but Apple hasn't tried to reproduce the iOS touch interface in OS X, and our experience with the Windows 8 touch interface makes me grateful that Apple isn't going to encourage me to jab at my laptop screen the way Microsoft wants me to.

The Cloud is Everywhere

Apple introduced its iCloud cloud-based synchronization and storage system, but Mountain Lion is the first version of OS X that was built around it. If you've already set up an iCloud account, Mountain Lion effectively sets up your new Mac for you a few moments after you first start it up. You enter your Apple ID and password, and Mountain Lion downloads your mail settings, contacts, Safari bookmarks, messages, iTunes backups and other features from the cloud. When you launch the App Store, all the apps you purchased earlier through the App Store are available for downloading and installation. Software Update, by the way, no longer exists as a separate app for updating OS X. There's still a Software Update item on the Apple menu at the upper left of the screen, but it opens the App Store, not the old Software Update app.

Mountain Lion builds cloud-based file storage into TextEdit and to updated versions of Pages, Numbers, and Keynote, and this feature may take some getting used to. When you open TextEdit, a menu lets you create a document to be stored either in your iCloud storage or on your Mac. The first time this menu appears, it defaults to showing you your iCloud storage, but a button lets you switch the display to a traditional Finder listing, and the program remembers which you prefer.

If you store documents in the cloud, you can't access them through the Finder, only through the list of cloud-based documents that appears when you open a cloud-enabled app like TextEdit, Pages, or Preview. This means that documents in the cloud are accessed somewhat in the way that songs are accessed in iTunes—you don't open them directly in the Finder, but through a simplified interface that only shows you documents that the current app can work with.

The traditional file system is opaque to most users, and even experts get impatient with it, and, as the amount of digitally-stored data increases, some system like Apple's is likely to supplant it in the future. Meanwhile, Mountain Lion does a reasonable job of helping users navigate between two radically different ways of storing documents.

Upgrades and Innovations

I tested Mountain Lion on two Macs, a 2011 MacBook Air with the Mountain Lion system that I've used continuously for the past year (since it was released in preview), and a new MacBook Pro with Retina Display, with Mountain Lion newly installed. When I upgraded from Lion to Mountain Lion on the MacBook Air, I was impressed by the smoothest upgrade I've ever experienced. When the computer restarted, OS X looked exactly as I had previously customized it, and a message told me that only two of my apps had been quarantined as incompatible. (One was the GlimmerBlocker ad-blocker, which worked perfectly when I installed the latest version. The other was an online security app used by some banks. Both installed successfully in Mountain Lion when I downloaded the latest versions of them.)

All my existing apps and utilities worked without a hiccup when I started them up in Mountain Lion. I haven't encountered any significant glitch after a week of heavy use, and, for the first time, I would recommend upgrading to a new version of OS X on its first release, instead of waiting for the first point release.

The most obvious new interface feature in Mountain Lion is the Notification Center hidden under a menu bar icon at the upper right of the screen. Just as new messages, scheduled events, and emails are signaled by notifications on the home screen in iOS, now these and much else can be signaled by boxes that appear briefly at the upper right of the screen (long-time users of the third-party Growl notification system already know where to look). Click on the menu bar icon or swipe the trackpad, and the full Notification Center slides open as a vertical panel on the right, showing all recent items. Click on any one to open it in its native app like Mail or Messages. Option-click on the menu bar icon to turn notifications on or off, or swipe down in the Notification Center to turn them off for the rest of the day. You can expect third-party developers to plug their apps into Notification Center, and I'm impatient for someone to support notifications of RSS feeds, because Apple—in the only change I dislike in Mountain Lion—removed built-in RSS support from Safari and Mail.

Sharing and Speaking

The most pervasive new feature involves sharing and social networking. A new "share sheet" feature accessible from Safari and Preview—and soon from third-party apps—lets you send a Web page or file via email, text message, Twitter (and you can choose among multiple Twitter accounts), Flickr, and OS X's built-in Air Drop local sharing system. After a forthcoming update of Mountain Lion, Facebook sharing will also be accessible (no word on when). The share sheet feature consolidates the old cluttered system where every app had its own menu items for sending or sharing, and it's designed to be extended through an API by future services and apps. It's a typical example of Apple's intelligent way of adapting its existing OS for the future without disrupting the existing interface.

The new dictation system is surprisingly accurate and flexible, and lets you add punctuation and symbols by simply saying, "at sign," "question mark," and other names. It sometimes drops words when transcribing a fast-talking New Yorker like me, but it's already quite good, and I expect improvements with every new update to Mountain Lion. The interface is slightly confusing: after enabling dictation in System Preferences—it's switched off by default—you click wherever you want your dictated text to appear, then press the Fn key twice and start talking. A microphone icon appears, with a button that says "Done." At first I thought the word "Done" meant that the system thought I was finished talking, but I soon figured out that I was supposed to click on "Done" when I was done talking. At this point, the system pauses for a moment to process your speech, and then types it on screen.

One note: When you enable Dictation, you authorize Apple to upload everything you dictate, plus your full contact list so that it can learn to recognize names, nicknames, and addresses. I was able to dictate contact names in Mail and Messages, though I sometimes had to learn to pronounce names in a way that was closer to the way they're spelled than I'm used to saying them. I learned quickly not to dictate in a noisy room: When someone was typing a few feet away, the system translated the keyboard noises into a kind of surrealist poetry in the middle of my ordinary sentences, and the dictation system thought I said the words "about the bathroom" when I wasn't even thinking about it.

Games, Security, and Fine-Tuning

Mountain Lion's Game Center feature went live only when the OS itself was released today, so I didn't get a chance to test it. But anyone who used Game Center on an iOS device will find the same features in the OS X version, including notifications when an invitation arrives to join a game. Game Center, combined with AirPlay Mirroring for displaying a game on an HDTV, makes me think that a lot of game consoles are going to start gathering dust when Mac users discover that their laptop now doubles as one of the most powerful consoles on the market.

New security features in Mountain Lion are designed to protect unsophisticated users while making it easy for experts to avoid inconvenience. By default, the new Gatekeeper system prevents any downloaded app from running unless you got it from the App Store or it was created by a registered Apple developer. If you want to run any other downloaded app or utility, you can control-click the app, choose Open from the pop-up menu, and confirm that you want to approve the app for your system; you only have to give this approval once, and OS X then lets the app run normally whenever you launch it. No dialog box explains this control-click trick, so your overly-trusting uncle won't be able to use it to install malware. If you have an administrative account on your Mac, you can simply turn off this system and run apps downloaded from anywhere. Gatekeeper doesn't block apps installed from CDs or USB sticks, but Apple silently downloads updated malware signatures to OS X systems to help the OS prevent any damaging software from running.

As always with OS X upgrades, some of the most welcome changes aren't the big ones that Apple trumpets on its website. Everywhere you look, you'll find small improvements in clarity that will make OS X easier to use for beginners while not getting in the way of experts. For example, when Safari starts downloading a file, an animated icon jumps from Safari to the Downloads icon on the OS X dock, and a small progress bar appears beneath that icon. Unlike Windows, where even experts sometimes wonder exactly where to find a downloaded file, OS X shows you exactly where the download is going and displays download progress without opening an additional window on screen. You get more information and less clutter. Of course, the traditional Downloads sheet is still available, but you probably won't bother opening it.

Under Lion, I never used the Launchpad feature (which displays icons of all my apps, like the home screen on iOS) because I had too many apps to waste time hunting them down in Launchpad. But under Mountain Lion, Launchpad has a search box that zeroes in on an app as I type its name, without finding similarly-named files like Spotlight does, so Launchpad has suddenly become as useful to experts as it is to beginners.

One small detail that combines usability and wit: While a file is in the process of being downloaded from Safari, the Finder lists its file date as January 24, 1984, which happens to be the date when Steve Jobs demo-ed the original Macintosh, but is also so far in the past that the download stays at the foot of a date-arranged file list so users won't be tempted to mess with it until the download is complete and the Finder gives it its actual file date.

Minor Annoyances, Major Successes

Some Mountain Lion improvements aren't visible unless you know where to look. For example, I'm one of countless users who grumbled when Lion took away the "Save As..." menu item from Apple's built-in apps like TextEdit and the iWork suite, probably because it confused users who thought the existing version of a file was going to be renamed when they used Save As. I was getting ready to grumble that Mountain Lion didn't bring back Save As, when I remembered the first rule for expert Mac users—always hold down the Option key and see what happens. Sure enough, when I held down the Option key in TextEdit and other Apple apps, the Save As item magically appeared in the File menu, along with the Duplicate item that Apple added in Lion as a replacement for Save As.

As it turns out, the Duplicate item is also improved, as you can now rename the duplicated version of the file instantly, because its filename is highlighted in the title bar and can be changed simply by typing in the new name.

I found fewer annoyances in Mountain Lion than in any OS I've used, and the most annoying is also the most easily fixed. Web pages in Safari won't display scroll bars by default, and so, until you tap the touchpad with two fingers, you may see no visual cue that the page extends below the bottom of the screen. Fortunately, you can fix this in the very first menu in the System Preferences app: just set "Show scroll bars" to "Always" instead of "Automatically based on mouse or trackpad."

Also, I was surprised by a few small inconsistencies that remain in the OS X interface. For example, in Mail, if you decide not to save or send a message, you can use either Cmd-D or Cmd-Delete as a shortcut key to get out of the Save dialog. But if you decide not to save a TextEdit document, don't press Cmd-D, because that selects the desktop as the selected destination for the file you don't want to save. You need to remember to press Cmd-Delete instead. Keep in mind that these are my biggest complaints about Mountain Lion, and they're trivial compared to my catalogue of complaints about Windows 8—which, it's worth noting again, is still in preview.

The Best OS is X

Year after year, we're more and more impressed by OS X, and Mountain Lion continues Apple's tradition of building on its strengths, innovating wherever it needs to, yet preserving continuity wherever it can. OS X 10.8 Mountain Lion is our Editors' Choice among desktop and laptop operating systems, and it looks likely to retain the distinction for some time to come.

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