A small but important tip.

In Mountain Lion, when you hold down a key, an iOS-like accent popup will appear.

Accent popup example

This feature is really annoying if you, like me navigate files in Sublime Text 2 running vintage mode. What I want is the key to repeat the letter, and luckily there's an easy fix for that.

To disable the pop-up simple run this command in your terminal:

$ defaults write -g ApplePressAndHoldEnabled -bool false