Mountain Lion is available from the Mac App Store here: http://itunes.apple.com/au/app/os-x-mou ... 6512?mt=12 Price $20.99 New Features: Messages: allows you to send and receive iMessages to and from iphone, ipad and macs. Also conversations sync automatically between all your iDevices iCloud: Ability to sync Documents between your devices through the internet, including syncing of reminders/notes made on all your devices safari: new safari with iCloud tabs. All the tabs you have open you can access on your other devices Notification centre: similar to the notification centre that was brought in with ios 5, a centralised place to see notifications from all your applications, which can be accessed at any time in OS X. (This will only work properly once apps are updated to support it) sharing: streamlined sharing abilities from within applications. Ability to share to mail, imessage, airdrop (other devices on your network), facebook, twitter, flickr, vimeo etc. game centre: similar to game centre on ios. play games against people on other iDevices, not just macs but any iDevice Improved Dictation (talk 2 text) Airplay mirroring: display your macs screen on your TV (requires a 2nd gen or newer Apple TV device, also requires imac mid 2011 or newer, mac mini mid 2011 or newer, macbook air mid 2011 or newer, macbook pro mid 2011 or newer) Power Nap: keeps your mac up to date while asleep (requires mid 2011 or newer macbook air, or macbook pro with retina display) Improved security: gatekeeper allows you to limit what gets installed on your computer by disallowing apps that aren't digitally signed, lowering exposure to apps that will compromise your computer. This feature can be disabled