Remove the Auto-Hiding Dock Delay in Mac OS X
If you use a hidden Dock in Mac OS X, you can speed up the time it takes to show the Dock with a defaults write command. This command removes the delay from when a cursor is hovered near the Dock location and to when it’s displayed, it doesn’t change the animation speed of the dock sliding in and out itself.
Remove the Delay for Auto-Hide & Auto-Show of Dock in OS X
Launch the Terminal and enter the following defaults write command:
defaults write com.apple.Dock autohide-delay -float 0 && killall Dock
The tail end of the command includes killall which will cause the Dock to relaunch in order for changes to take effect. After it has been refreshed, hover over the area of the screen where the Dock is hidden and you’ll notice it shows up immediately, without the fraction of a second delay.
This tip also impacts how to show the Dock in a full screen app, preventing the need for a double-swipe down when in full screen mode, and instead displaying the Dock instantly with a hover in the region.
Return to Default Dock Hide/Show Delay
To return to the default setting and autohide delay, go back to the Terminal and enter the following command:
defaults delete com.apple.Dock autohide-delay && killall Dock
The Dock will again relaunch and settings will return to their default state.
This trick works in all modern versions of OS X, including Yosemite, Mavericks, and Mountain Lion.
This is a handy tip from MacWorld, thanks for sending it in Eric