There's a good reason that people use the word "ecosystem" when discussing Apple products.

Indeed, the company has spent the last couple of years pushing the idea that customers should have the same user experience regardless of which device is in their hands. And now, just as iOS has evolved to unify that experience across the iPad, iPhone, and iPad Touch, the latest version of OS X brings the Mac further into the fold.

Announced today as Mountain Lion (v10.8), the update brings many of the features born in iOS 5 and plants them on the desktop. Some of the additions, like Notes, Reminders, and iMessage, are strictly functional, while others, like AirPlay Mirroring, iCloud, and a deep Game Center integration, spread the content love across your Apple-integrated universe. And don't assume that Mountain Lion just rehashes what you've already seen, for it also delivers a new security feature that keeps Apple at the forefront of malware protection.

Since we're nowhere near the final version of Mountain Lion (that will come this summer), I won't have an official CNET review or performance benchmarks quite yet. But after using an early preview of the developer release for a few days, I can walk you through 10 feature highlights and describe the user experience. To someone who's covered the iPhone and iOS since that very first handset five years ago, it was abundantly clear what Apple is trying to do here. In fact, from the moment I cracked open a MacBook Air with Mountain Lion onboard I was in familiar territory.

We'll expand on this First Take over the next few months as Apple announces more features. And as you read on, keep in mind that the interface that I'm describing here may change at any time. Once the customer release of Mountain Lion climbs into the Mac App Store, though, you can rest assured that we'll pull out all the review stops.

Though hardly glamorous or shiny, iMessage was one of the better features of iOS 5. It provided yet another way to keep in touch, and because it lived outside of your wireless carrier's realm, you could send everything from text to photos without adding a penny to your cell phone bill. Seriously, who doesn't love that?

Granted, bypassing your carrier's clutches isn't a concern when messaging on a Mac, but Mountain Lion's iMessage app is just as easy to use. You'll find all of the same features, including delivery and read receipts, encrypted messaging, support for media and contacts, and a typing indicator. You can send messages to an iPhone number or e-mail address (assuming your friend's device also has iOS 5 or Mountain Lion) and you can talk to a group at once. And thanks to iCloud, your chats are pushed to all of your Apple devices.

As iMessage replaces the iChat app, you'll need an Apple ID to get started. The interface is largely similar to the mobile experience while showing a few differences such as a list of chats on the left side and a longer conversation display. I loved that you could launch FaceTime from the app, though I'd prefer a button for adding photos directly into your conversation (like you get in the messaging app on the iPhone). Yes, you can open a photo on your desktop and drag it over to your chat window, but that involves a couple of additional steps. Hopefully, Apple will address this in the final version of Mountain Lion.

Another iOS 5 import, the Reminders app also brings the same features while adding a few more goodies. You can make a to-do list, set due dates for alerts, and push your information to all devices. Thanks to your Mac's larger display there's also a search field for finding buried reminders and a calendar for viewing reminders tied to a specific date.

The only feature not carried over from iOS 5 is the ability to set a geofence for a task. That means, of course, that you can't set your Mac to remind you to "call home" when you leave work and then receive the notice when you're out the door. I don't think that's a huge loss, but it's worth pointing out just the same.

Here again, though the basics of typing a note are unchanged, the interface has been modified and enhanced for use on a Mac. Now you can use rich text, make bullet or numbered lists, search for notes, and add a photo. Adding links is a promised feature, as well, though I wasn't able to use it at the time of this writing. There's also a sharing app for sending a note via e-mail or iMessage and you can pin a note to your desktop to keep it always visible. And just like with iMessage and Reminders, you can see a list of all Notes on the left side of the app and you can push content to all devices linked to your iCloud account.

Apple took a big step forward when it introduced the Notification Center in iOS 5. As Android fans will point out, the pull-down menu wasn't novel, but it did improve the user experience immensely. And with Mountain Lion, Apple has carried the feature over to the Mac while shaking it up a bit.

You start by configuring notifications in the Systems Preferences menu. The feature works with a broad assortment of apps, including e-mail, iMessages, missed FaceTime calls, Twitter mentions and direct messages, event reminders, and calendar invites, but you can select only the apps that you want to use. When notifications and alerts arrive they'll appear in the top right corner of your screen. The former will disappear after 5 seconds while the latter will stay on the screen until you dismiss them.

To access the full Notification Center, just slide two fingers across the trackpad from its right edge. You'll then see your full notifications list on the right side of your screen. Only the five most recent notifications from each app are visible (you can choose to view fewer) and you can dismiss them by clicking the box on the right side (similar to iOS). Fortunately, you can access the Notification Center from anywhere on your Mac.

Twitter integration
Granted, this may not sound exciting if you don't use Twitter, but it does further demonstrate Apple's unifying intentions with Mountain Lion. As with iOS, you now can tweet directly from a variety of apps as long as you've integrated your Twitter account. I used it with Photo Booth and Safari, but it also works with Quick Look and Preview. The user experience was seamless and worked just as it does on iOS.

You also can add a location and integrate your list of Twitter pals with the profiles in the Contacts app. Still to come is Mac App Store integration so you can tweet a link to an app directly from the store.

iCloud integration
As the first major Mac OS release since the introduction of iCloud, Mountain Lion opens access to cloud-based features so you can keep up with important info on all your devices. As mentioned, Notes, Reminders, and iMessages created on your Mac will be synced with other devices. And in turn, when you initiate those apps on a mobile device like an iPad or iPhone, the content will appear on your Mac.

A couple of iCloud features will not be available in the developer version I used, but Apple says they are coming soon. First off will be the ability to view, create, and edit the same iCloud documents from your iPhone, iPad, or Mac. Any changes made on any device will be reflected on all devices through iCloud. Also coming is a new Document Library that will launch with apps that support Documents in the Cloud. Besides giving you access to your latest documents regardless of where they were created, it'll mean you'll also be able to create Document folders in much the same way you create folders on iOS (drag and drop a document on top of another). You'll also have a Share button built in to the Document Library so you can quickly send a document via Mail, Messages, or AirDrop.

Game Center
The gaming hub that has been a big success on iOS devices, with more than 100 million registered users, will now be available for Mac in Mountain Lion. Though it is not yet available in my preview of the new OS, Apple says you'll be able to set up and personalize your gaming experience with a Game Center app for Mac. As with the iOS app, you'll be able to view friends already in your gaming network and discover new gaming fans through Game Center recommendations.

Apple says that Game Center for Mac will come with all the bells and whistles found in the iOS version, including the vast user base already registered for the service. You'll be able to discover new friends; browse games your friends are playing; view leaderboards to see how your scores match up; and earn achievements in games across all your devices. You'll also be able to play multiplayer games across all your devices (with friends or automatched opponents), participate in in-game voice chat, and receive Game Center notifications. Apple says the Game Kit for developers will include tools for creating multiplayer games that can be played on a Mac or your favorite iOS device.

Share Sheets
While I'm on the subject of sharing, Mountain Lion adds an easy way to share photos, videos, and links from within an app. After clicking the share icon imported form iOS, you'll be able to create Share Sheets and then pass on the content via Mail, message, AirDrop, and popular third-party social-networking sites.

I like that the Share button detects the file type selected and only lists sharing options that are appropriate for that file type. So if you're looking at a Web page in Safari, for example, you'll have options to share via e-mail, Message, or Twitter. While Share Sheets are not a groundbreaking new feature, they will obviate the need to drag files or links to other apps before sending. Apple says that the Share Sheet API will let developers take advantage of sharing services as well, so people will able to share with others using third-party apps with a consistent and convenient interface.

AirPlay Mirroring
I hate to use the word "ecosystem" again, but that's definitely what this feature is all about. With AirPlay Mirroring, you can take what's on your Mac and present it on an HDTV via Apple TV. The video stream is 720p and it will match the resolution of the external screen that you're using. Apple hasn't activated this feature yet so I wasn't able to use it, but it sounds very cool.

In an app-centric universe, security concerns continue to evolve beyond the common question of whether you should download that attachment in an unfamiliar e-mail. Fortunately, Apple's app stores both for the Mac and iTunes have always offered a deep level of protection, but a new feature called Gatekeeper spins it in a new direction.

In addition to existing OS X features like download validation and blocklists, Gatekeeper lets users choose where their apps can originate. If you don't want to take any chances, you can choose to allow apps only from the Mac Store, but if you're looking for more freedom you can designate all third-party apps as acceptable. You can mark your selection in the Security & Privacy menu in System preferences.

Most people, however, don't see things just in black and white, which is why I think the third option will be the most popular. Smack in the middle of the two extremes, it lets users download all apps from the Mac App Store and all third-party developers that are signed with an Apple Developer ID. Any approved Apple developer can obtain an ID, which the developer can assign to titles that live outside Apple's stores. Then, when Mountain Lion detects a Developer ID on a third-party app, it will confirm that the title is not malware, that it has not been tampered with, and that the developer is not known to have distributed malware.

For the security-conscious (which, in all seriousness, should be everyone), the Developer ID is an impressive step forward in protection. Screening the apps in your own store is one thing, but adding the ability to track titles living elsewhere is quite another. What's more, it's a step that none of Apple's rivals are taking. Of course, there are some obvious concerns such as whether an ID is still tracked if the developer leaves Apple's program. Apple hasn't answered that question yet, but I imagine that we'll get more information in the final release.

When Apple announces a new "cat" with an OS X upgrade, you know that it's about more than just bug fixes and interface tweaks. With Mountain Lion, the same rule applies. Though most of the features (Gatekeeper being an obvious exception) are familiar and not monumentally significant, the upgrade significantly changes the user experience. By bringing iOS features to the desktop, unifying the interface, and pushing your data to multiple devices, it marks a closer union between the Mac and Apple's mobile devices. And as CNET's Scott Stein will tell you, that's something that we've needed for a long time.

As mentioned, we'll save making our final assessment of Mountain Lion until we get the final version. But even in this early preview, it's clear what Apple's intentions are. Sure, I'd like a few changes, but it is the right course to take. Even better, Apple appears to be on the road to accomplishing it.