Downloads of Apple’s OS X Mountain Lion have exceeded 3-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 desktop operating system and is available through the Mac App Store as an upgrade to Lion or Snow Leopard users for $19.99.

“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,” says Philip Schiller, Apple’s senior vice-president: worldwide marketing.

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