Apple today announced that downloads of OS X Mountain Lion have exceeded three million in four days, making it the most successful OS X release in Apple's history.

With more than 200 new features, Mountain Lion is the ninth major release of the Apple's desktop operating system and is available through the Mac App Store as an upgrade to Lion or Snow Leopard users for $19.99 (US).

"Just a year after the incredibly successful introduction of Lion, customers have downloaded Mountain Lion over three million times in just four days, making it our most successful release ever," said Philip Schiller, Apple?s senior vice president of Worldwide Marketing.

Mountain Lion features include the all new Messages app, Notification Center, system-wide Sharing, Facebook integration, Dictation, AirPlay Mirroring and Game Center. iCloud integration makes it easy to set up your Mail, Contacts, Calendar, Messages, Reminders and Notes, and keep everything, including iWork documents, up to date across all your devices.