Let's have a look at the GUI, concentrating on details that Steve did not mention; despite the fact it will come up immediately the first time you will launch Leopard 10.5: new Finder and new desktop.
The desktop has been redesigned. The menu bar is now transparent, and the dock can be displayed with a rather nice projection effect applied to both icons and windows. The long rumored stacks are finally there, after having been filed and patented by Apple. You can now drag and drop several documents together in the dock to associate them as a stack. By clicking on the representative icon, you will deploy the stack and be able to click the one you need. downloaded files with Safari as well as attached files in mails will automatically be piled up in stack in the dock.