Apple has announced that the Mountain Lion operating system has hit 3 million downloads in its first 4 days. This means that it is the most successful OS X release in Apple’s history. Mountain Lion was released last Wednesday as a $19.99 download from the Mac App Store. Users that buy the operating system will allow customers to download the OS on multiple computers that have the same Mac App Store account. Last year Apple served one million downloads of OS X Lion in 24 hours. Apple Mountain Lion has an iOS-style Notification Center, AirPlay Mirroring, and iCloud support.