Apple's recently released OS X 10.8, codenamed Mountain Lion, is officially the California company's most successful OS X release to date. Totalling more than three million downloads in its first four days of availability, it overshadows OS X 10.7 Lion — the prior version of the operating system, which was also the first to be made available via a direct download from the Mac App Store. Lion was already the fastest-spreading OS X upgrade in Apple's history, thanks to that direct distribution method, and the cheaper and universally better Mountain Lion seems to be keeping that momentum going.