Apple has announced OS 10.8 Mountain Lion, the latest update to their Mac OS X operating system. Mountain Lion follows the trend begun with OS 10.7 Lion of bringing popular features from the iOS mobile operating system back to the Mac.

The beta version of Mountain Lion is available to developers today, with a public release this summer. The new operating system brings a slew of popular iOS features to Apple’s computers. Mountain Lion will be getting the Notes and Reminders apps, as well as Game Center integration, the Notification Center, OS-level Twitter integration, and the Messages app.

The public release of Mountain Lion is scheduled for “late summer 2012.” Mac users who want a taste of things to come, though, can check out the beta version of the Messages app, available for download today from Apple’s website. Message will replace iChat, and will retain integration with chat services like AIM, Google Talk, Yahoo! Messenger, and Jabber. It will also, however, integrate with the iOS version of Messages, allowing users to send pictures, videos, and SMS messages from their Mac to any iOS 5 device for free. Messages is currently available from Apple’s website, and is not in the Mac App Store yet.

Speaking of the Mac App Store, Mountain Lion also comes with what Apple is calling “a revolutionary new security feature.” Gatekeeper gives users control over what can and can’t be downloaded and installed on their Macs. While Mac users can currently download and install apps from anywhere, just as PC users can, Gatekeeper allows users to control where apps come from. While it includes a setting to allow apps to be installed from any source, the default setting is to allow apps from only from the Mac App Store and from developers with developer IDs from Apple. It also allows a stronger lockdown feature that will permit only apps from the Mac App Store, effectively duplicating the somewhat controversial “walled garden” ecosystem in place on iOS.

Mountain Lion also brings some long-awaited features and fixes to OS X. Since iCloud launched late last year, users have complained that the service’s interface with Lion was problematic. Mountain Lion apparently tightens and improves iCloud integration. Mountain Lion also brings AirPlay mirroring to the Mac, allowing users to send video from their Macs to their iOS devices, including the Apple TV.

For more information on Mountain Lion, you can check out Apple’s sneak peek page here. Expect more information about the new OS – and maybe even some hints about other upcoming Apple products – as developers dig into Mountain Lion’s code.

What do you think of Mountain Lion? Check it out and let us know in the comments.