Mac OSX ships with very slow key repeat rates (how quickly a key repeats after it is first pressed, and how quickly a key input repeats after holding it down). Changing these effectively is not possible in System Settings, we instead use the command line.
First, read the two relevant values in case you want to go back:
defaults read -g InitialKeyRepeat
defaults read -g KeyRepeat
changing these values is similarly easy:
defaults write -g InitialKeyRepeat -int 12
defaults write -g KeyRepeat -int 2