Mac OS X Snow Leopard
Interface enhancements like Expose in the Dock and better file and folder viewing in Stacks make finding apps and files much easier. A completely overhauled QuickTime X now sports a cleaner interface and recording tools. The much-anticipated Exchange support across Mail, the Address Book, and iCal is huge for those who take their Macs to work.
Apple says a few new technologies in Snow Leopard make it worthy of the upgrade alone, with several features that Apple says will boost performance. Because all new Macs come with 64-bit multicore processors, multiple GBs of RAM, and high-powered graphics processing units, all the major applications in Snow Leopard--including the Finder--have been rewritten in 64-bit to take full advantage of the hardware. (The 64-bit technology allows application developers to allocate more memory to complete tasks so that the software runs faster and more smoothly.)
Apple has also added what it calls the Grand Central Dispatch that manages data sent to multicore processors in an effort to maximize performance; Apple says the GCD will speed up any application task, from processing images in Photoshop to playing your favorite games. The addition of the GCD also takes away the need for software developers to spend as much time managing multicore processors.
Another new technology in Snow Leopard is OpenCL, which allows software developers to tap into the power of any onboard video cards (or GPUs, for graphics processing units) for general-purpose computing without the addition of enormous amounts of code. Like the GCD, these are improvements that will mainly affect software developers. But hopefully it will mean more and better-performing software for users in the future.