Change the Dock item click-and-hold behavior in Snow Leopard
Snow Leopard changed the way the Dock behaves when a Dock item has been clicked on and held down, since 10.6 it launches Expose for that specific application. You may recall how Leopard handled the click-and-hold though, which was to launch the contextual menu (the same one you get when you right-click in 10.6). Using the Terminal and the defaults write command, you can alter this behavior between the 10.5 contextual-menu and 10.6 Expose style click-and-hold Dock behavior. So launch your Terminal:
Show contextual menu rather than Expose when Dock item has been clicked and held (like 10.5)
defaults write com.apple.dock show-expose-menus -bool no; killall Dock
Revert to Expose upon click-and-hold (10.6 default)
defaults write com.apple.dock show-expose-menus -bool yes; killall Dock
I actually like the new Expose click effect (which is slightly different in 10.6.2 than it is in 10.6), so for me this is a matter of “If it ain’t broke, don’t fix it” but to each their own.
via Lap Cat Software