Make middle-click on app icon in dock show app window exposé once more In earlier versions of OS X (Snow Leopard, maybe?), middle-click on an open application's icon in the Dock would have the same effect as right-click -> show all windows.

In (Mountain) Lion, this is no longer the case. Middle clicking on the icons in the dock has no effect whatsoever.

Does anyone know how to bring this functionality back?
I didn't find any hidden preferences for it with gdb, but there is a preference that makes scrolling up show all windows:

defaults write com.apple.Dock scroll-to-open -bool true
killall Dock