The bits I'm really looking forward to in Snow Leopard.
From http://www.apple.com/macosx/refinements/enhancements-refinements.html
The Finder has been completely rewritten using Cocoa to take advantage of the new technologies in Snow Leopard, including 64-bit support and Grand Central Dispatch. It’s more responsive from top to bottom, with snappier performance throughout the Finder.
Snow Leopard makes ejecting external drives more reliable. Core system services such as Spotlight indexing and file system events will intelligently stop their work so you can remove your drive. And improved dialogs tell you which applications are using the drive so you know what to close in order to safely disconnect your drive.