By Matt Swain Here are a couple of tips for customising the delay and animation speed of your Dock if you have it set to automatically show and hide (in System Preferences).

Custom delay time

You may have noticed that there is a short delay before the Dock appears when your mouse hits the edge of the screen. There is a hidden setting that allows you to adjust the delay time using the Terminal.

Start by opening up the Terminal app (in Applications/Utilities). To remove the delay entirely, paste in the following line and press Return.

defaults write com.apple.Dock autohide-delay -float 0

The changes won’t take effect until you restart the Dock, which you can do by typing killall Dock and pressing Return.

The number at the end of the command is the delay time in seconds, which you can customise to your liking. My preferred delay is 0.1, which is a bit quicker than the default. To return to the default, just use the following command:

defaults delete com.apple.Dock autohide-delay

Custom animation speed

There is a related hidden setting that allows you to customise the speed of the animation when the Dock slides onto the screen. As before, paste the following line into the Terminal and press Return.

defaults write com.apple.dock autohide-time-modifier -float 0.5

Remember to restart the Dock with killall Dock for the changes to take effect. Just like the delay, the number at the end is the length of the animation in seconds. 0 will make the Dock instantly appear with no animation. My preferred time is about 0.5, which makes things just a little snappier than the default.

To return to the default, just use the following command:

defaults delete com.apple.Dock autohide-time-modifier

Source: Mac OSX Tips