Although positioned as an under-the-hood upgrade to Leopard, Mac OS X 10.6 Snow Leopard offers a lot of changes on the surfaces as well. Under the hood, it offers a 64-bit OS for faster processing and greater memory access, support for multicore processing via Grand Central Dispatch and OpenCL, and faster Java and QuickTime performance.
Do note that Snow Leopard does away with two old Apple technologies: It no longer supports the long-waning AppleTalk network protocol, and it won't run on PowerPC-based Macs. If you have PowerPC apps (such as the Microsoft Office Update utility), note they will run if you have Apple's Rosetta technology installed. If Snow Leopard may not install Rosetta automatically, you can install it using the Optional Packages installer on the Snow Leopard installation DVD.
