While you wait for that order to ship, Apple wants you to know that Snow Leopard's Finder is more responsive, Mail loads messages twice as fast, Time Machine will complete initial backups 80 percent faster, and a 64-bit version of Safari 4 is 50 percent faster than its predecessors. There's even QuickTime X with a redesigned player that lets users view, record, trim and share video. Of course, this release also includes Grand Central Dispatch, a new way for devs to take advantage of multi-core processors as well as OpenCL support to accelerate apps with the help of that idling graphics processor. Oh, and out of the box support for Microsoft Exchange too. All in all, a worthy update, especially for the price.
P.S. Requires Intel-based Mac.