I’m not kidding: Apple disabled keyboard repeat for all keys but cursors in MacOS X 10.7 (Lion) for most apps (e.g. not in Terminal).
What should you do if you have to write something like: “Aaaaaaaaaaaaaaaaaaaah, this sucks!” Well, you could type ‘a’ a dozen times. Or you type:
defaults write -g ApplePressAndHoldEnabled -bool false
(Note: This works for apps started afterwards, only)
Thanks to wikiHow for making the defaults command appear on my Google search.