The sixth incremental software release for Apple’s Snow Leopard operating system, Mac OS X 10.6.6 is available in both Client and Server form, and is recommended for all users running Snow Leopard on their Intel machine. To have the service installed on their Macs, customers must download Mac OS X 10.6.6, Apple said. As promised, Apple today rolled out the Mac App Store, a one-stop shop where over 1,000 paid and free applications can be downloaded immediately.