One thing I'd love to see added to Notification Center would be a section to track downloads and file transfers. Ever since Mac OS X supported Spaces and multiple desktops, locating the Finder's progress bar is sometimes difficult for me; Notification Center looks like the perfect location to consolidate those types of activities.
One of my all-time favorite iOS features finally makes it as a system-wide service to the Mac: AirPlay Mirroring. AirPlay allows any iOS device to broadcast video, audio or both to an AppleTV-equipped HDTV. On iOS devices, videos, games, music, pictures, presentations, podcasts, apps -- literally, anything -- can be broadcast to an AppleTV, wirelessly, at 720p resolution and 5.1 surround sound, at the push of a button with no configuration.
While AirPlay was limited to iTunes in previous versions of OS X, Mountain Lion adds AppleTV support in the Displays system preference. Like iOS, one can configure the AirPlay icon to appear when an AppleTV is located on the same network; and like iOS, the Mac will be able to mirror everything on screen (including audio).
Why is this a big deal now that this function is accessible outside of iTunes? Much has been written about Apple working out content deals with networks/cable providers/content creators to have content available on the iTunes store. But with AirPlay, that's no longer necessary. Most cable companies and networks now offer their shows online -- think HBO Go, Hulu, etc. -- and with AirPlay, you just call up whatever you want to watch on your computer, when you want it, and watch it on your TV via AirPlay. No content deals are necessary, no new TV is needed, and the whole ecosystem circumvents the current cable provider setup -- the sole exception being the need for broadband.
AirPlay in Mountain Lion could cause major disruptions down the line for several industries.
One of the more publicized changes in Mountain Lion is a new paradigm in which the operating system handles security, specifically regarding applications. Currently, OS X can install and run any application from anywhere; a warning pops up the first time an app is launched but that's all that stands in the way of that app running.
With the Mac user base growing, so, too, is the danger of malware. Granted, Mac Trojans and viruses are still a tiny blip compared to the malware written for Windows machines on a daily basis, but it's good to see Apple being forward-looking in its attempts to bolster system security, even if it means greater reliance on the Mac App Store. The App Store for OS X works like the iOS app store: curated, Apple-approved apps make it a safe place to purchase software without having to worry about malware.
Now comes Gatekeeper. Briefly, Gatekeeper is a new security paradigm in which one of three types of security modes are implemented. The first mode allows applications downloaded from anywhere to run -- it's an option literally called Anywhere in the "Allow applications downloaded from:" section of the Security Preference. This will let the Mac behave as it does now, with app installations from any source allowed with the proper permissions, at the user's discretion.
The second option allows for apps to be installed if they come the "Mac App Store and identified developers." This option allows digitally signed apps to run on your Mac. A digitally signed app gives Apple the right to revoke privileges for troublesome apps and track down responsible parties, as each signature is unique to developers. Applications that aren't signed won't be able to run when this mode is enabled.