There are a few key changes in Leopard to both the menubar and the contextual menu.
As you should already know the menubar is slightly translucent in 10.5, but there’s more the the story that isn’t as visible. First of all, since System Software 1.0 the top edges of the menubar were curved. 10.5 ends that long interface piece. Instead, the bottom of each menu is curved, unlike in the earlier OS versions. The help menus have a in-menu search equivalent to that of Spotlight’s. That searches the entire set of menus for the application as well as searching the application’s helpbook.
The contextual menu is curved on all ends. When you activate it, the part of the screen behind it gets blurred.