Mountain Lion

share unlimitedly
always handy
new feature like ichat where you can send unlimited messages between mac,iphone,ipad,ipod
not to forget!!
one place notification
Air Gaming!! compete between ipad and mac or with ipod or iphone
Mountain Lion is the new upcoming OS from Apple version 10.8 named ‘Mountain Lion’. Messages(beta) is a new feature in it where you can share unlimited messages between mac and tools running ios5 and yes it is available for download. icloud becomes more wide in its usage and you create in one and access everywhere through it through your apple id….
Developer Preview Available and if you want to develop apps for the same you can go ahead and download it from www.apple.com 
notice the yellow highlighted box to know more about mountain lion (Apple site)
Source : Apple