Apple - OS X Mountain Lion - See everything the new OS X can do.: These are the 2 most killer new features of Mountain Lion - AirPlay Mirroring and Dictation.
AirPlay Mirroring
Wireless mirroring
Send what’s on your Mac screen to an HDTV wirelessly with Apple TV. Mirroring is great for classrooms, conference rooms, and your living room.
High definition
AirPlay Mirroring sends a video stream automatically optimized for the HD capabilities of your Mac and Apple TV. It supports up to 1080p HD.
Automatic detection
When a Mac with Mountain Lion detects an Apple TV on the same network, the AirPlay Mirroring menu item appears in the menu bar.
Menu item
To wirelessly mirror your Mac to your HDTV, click the AirPlay Mirroring menu item and choose your Apple TV. Use the menu to select a different Apple TV on your network and set resolution matching.
Resolution matching
AirPlay Mirroring scales the contents of your Mac desktop to fit on your HDTV. For a sharper image, choose to set the resolution of your desktop to best match that of your Apple TV.
Seamless integration with iTunes
When you play movies or TV shows with iTunes on your Mac, AirPlay Mirroring will automatically switch to a full-screen AirPlay experience on your HDTV.
Encrypted streaming
AirPlay Mirroring uses encryption to securely send what’s on your Mac to your Apple TV.
Audio support
With AirPlay Mirroring, audio from your Mac is wirelessly sent to your Apple TV. You can use this feature independent of AirPlay Mirroring by selecting your Apple TV in the Sound pane of System Preferences.
High performance
AirPlay Mirroring takes advantage of advanced hardware video encoding to deliver high-definition mirroring efficiently and optimize processor use.
Dictation
Talk anywhere you can type
OS X now supports Dictation. So wherever you can type, you can use your voice instead. Just select a text field and turn Dictation on. Use the keyboard shortcut — press the Function key twice — or choose Dictation from the Edit menu in any app. When you’re finished speaking, click Done. Dictation converts your words into text.
Works with any app
Dictation works with text fields in any OS X app — no additional third-party developer support is required.
Works with Contacts
Just say your friend’s name, and Dictation knows who you mean. It works with information in the Contacts app to recognize and spell names accurately, even if they have unusual spellings.
Keyboard shortcut
Press the Function key twice to start Dictation. Press it twice again when you’re done speaking.
No setup or training required
No setup or special training is required. Dictation just works. The more you use it, the better it understands you. Dictation learns the characteristics of your voice and adapts to your accent.
Works out of the box
Dictation uses the built-in microphone on your Mac, so it works as soon as you start speaking. You can also use an additional microphone.
Dictate commands
Dictation understands basic text-related commands such as “all caps,” “new paragraph,” and “new line.” When you say “period,” “comma,” “question mark,” or “exclamation point,” Dictation punctuates for you.
Languages
Dictation supports English (U.S., UK, and Australia), French, German, and Japanese. When your system is set to one of these languages, it automatically enters the right text.