One of Snow Leopard’s new features is Dock Exposé–clicking and holding on an icon in the Dock will enter Exposé‘s Application mode for that application (highlighting windows for the chosen app while dimming all others), and display a limited pop-up menu above the Dock icon, showing just Quit, Hide, and Options.
Lost in this new functionality, at least apparently, is the ability to view the OS X 10.5-style Dock contextual menus–those that offer options specific to the program. In 10.5, for example, if you click-and-hold on the Mail icon in the Dock, you can check for new messages or compose a new message using the contextual menu that appears.
As you may have discovered already, you can still get these menus to appear in 10.6–you just need to Control-click on the Dock icon, instead of using click-and-hold. (This also works in 10.5, of course.) Once you get used to using a Control-click, I think this structure provides a good solution–you get the old behavior with one action, and the new behavior with another.
However, if you really hate Dock Exposé, it turns out you can completely disable it. Once disabled, both Control-click and click-and-hold will get you the 10.5-style contextual menus. To disable Dock Exposé, open Terminal (in Applications -> Utilities), and enter these two commands:
defaults write com.apple.dock show-expose-menus -bool no killall Dock
With that, Dock Exposé is gone–you can still see the limited Dock menus by manually activating Exposé‘s Application mode, but you can’t reach it directly from the Dock any more. If after trying this, you decide you prefer 10.6’s default behavior, run these two Terminal commands:
defaults delete com.apple.dock show-expose-menus killall Dock
Thanks to Mac OS X Hints contributor Swordfish> for sending this one in, and to Jeff Johnson of Lap Cat Software, who discovered the hidden preference to disable Dock Exposé.