In the App Store, the quiet App Store, Mountain Lion sleeps todaaaaay.

Yup, OS X Mountain Lion is currently available for download in iTunes, and if you've got a credit card, and $19.99, and the right hardware, you can update your Apple desktop or laptop right now. Just click on this shiny blue link to travel to the Mac App Store to start your download. After you hit the download button, you'll enter your Apple ID and the download -- about 4GB in all, or "about the size of a full-length film download," as CNET puts it -- will begin.

There are a few system requirements in order to download Mountain Lion from the App Store. First, you'll need to currently have OS X 10.6.8 Snow Leopard or higher on your Mac (here's how to check that). Second, not all desktops and laptops will be able to run Mountain Lion. Apple has supplied the following list of supported hardware:

  • iMac (mid 2007 or later)
  • MacBook (13-inch aluminum, late 2008, 13-inch early 2009 or later)
  • MacBook Pro (13-inch, mid-2009 or later), (15-inch, mid/late 2007 or later), (17-inch, late 2007 or later)
  • MacBook Air (late 2008 or later)
  • Mac Mini (early 2009 or later)
  • Mac Pro (early 2008 or later)

It's also a good idea to make sure all of your applications are up-to-date before you download Mountain Lion. Run the free Software Update (instructions right here) before you take the plunge and download Mountain Lion. For more on how to prepare your Mac for Mountain Lion, check out this guide put together by our friends at The Unofficial Apple Weblog (also owned by AOL) .

And that's it! Just a quick trip to the App Store, a $20 charge to your credit card, and you're done. Once you've got Mountain Lion, make sure to check out all the new cool features (Voice dictation! Notification center! Twitter!) and let us know what you think in the comments.

UPDATE: We've been asked on Twitter if you will be able to install Mountain Lion on multiple computers for free. You can! Here are the official instructions, via Apple, for how to do so. These instructions are for installations of OS X Lion but apply to OS X Mountain Lion as well.

Earlier on HuffPost:

A few Mountain Lion features teased by Apple at the Worldwide Developers Conference:
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  • Mountain Lion Messages

    iPhone users can respond directly on their Mac to messages received on their phone. The feature not only enables Mac-to-Mac and Mac-to-device messaging, but also saves the complete message history. (<a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">Image via <em>Engadget</em></a>)

  • Mountain Lion Notification Center

    "Sometimes when you're using a Mac it can have something it needs to tell you," Federighi said <a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">during WWDC 2012</a>. Similar to notifications on the iPhone or iPad, Mac users will receive instant alerts and notifications in the upper-right hand corner of the screen. However, oftentimes these notifications can be disruptive. With Mountain Lion, these messages will slide in and users can navigate back to the full list using two-finger gesture control. Users can also enable Internet notifications from websites like Twitter to pop-up in this fashion. (<a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">Image via <em>Engadget</em></a>)

  • Mountain Lion Sharing

    Support for sharing is built directly into the operating system so users can authorize specific apps and programs in order to seamlessly access and connect to social media services and networks. For example, in iPhoto, users can press the share button and instantly send a photo to a friend via Messages. (<a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">Image via <em>Engadget</em></a>)

  • Mountain Lion Safari

    Among the Apple browser's newest features, the new unified smart search field received the most applause. Users will be able to type in their search inquiry and Safari will bring up the best result using bookmarks, browsing history and other data. Safari will also be iCloud-enabled so that browsing history, bookmarks and even open tabs will be automatically synced across all devices. A user could effectively switch from their Mac to their iPad, picking up their browser where they left off. Federighi demonstrated Safari's improved usability with multi-touch gesture control. Scrolling is smooth and lightning fast and users can visually navigate through all of their tabs with the swipe of a finger just like in iTunes. (<a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">Image via <em>Engadget</em></a>)

  • Mountain Lion Dictation

    Although Mountain Lion will not have Siri -- not yet anyway -- the Mac OS is being revamped with its own voice dictation service. A user can talk directly into the microphone and Mountain Lion will dictate to Facebook, Microsoft Word or other third-party programs. (<a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">Image via <em>Engadget</em></a>)

  • Mountain Lion Power Nap

    Siestas are often necessary during the day, but that usually means time away from our laptops is time wasted. With Power Nap, a user's Mac will automatically update itself, fetch emails and auto-sync while its offline, enabling users to sleep easy. The feature will run quietly in the background, and boasts power efficiency. "We all love using our Macs, but wouldn't it be great if when we weren't using them they were still working for us?" Federighi said. <a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">during WWDC 2012</a>. (<a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">Image via <em>Engadget</em></a>)

  • Mountain Lion Airplay Mirroring

    With this feature users will not be hindered by bulky cables when they want to push something from their laptop onto their TV screen. Airplay Mirroring enables users to wirelessly push pixel-for-pixel 1080p content from an Apple laptop with Mountain Lion, <a href="http://support.apple.com/kb/HT5209" target="_hplink">or another device</a>, to a screen via Apple TV. Airplay will not only be limited to visual devices. Users can effectively send audio from their laptop to their stereo system. "We also support sending audio to AirPlay-enabled stereo systems and speakers," Federighi said during WWDC 2012. (<a href="http://www.engadget.com/2012/06/11/apple-wwdc-2012-liveblog/" target="_hplink">Image via <em>Engadget</em></a>)

  • Mountain Lion Game Center

    The platform will appear the same on Apple laptops as it does on a user's mobile device. Federighi showed off his racing skills -- or lack there of -- in an on-stage CSR Racing demo against a <a href="http://www.dailymail.co.uk/news/article-1123502/The-Stig-s-unmasked-Top-Gear-use-FOUR-different-mystery-test-drivers.html" target="_hplink">Stig</a>-like racer (any Top Gear fans?) Using both Airplay and Game Center, multiple players can participate in a game whether they are on a Mac or a mobile device. (Photo credit: AP)