I came into this last year (I think) and I found the solution somewhere and I added it to my personal notes. After a Mavericks reinstall I got the same problem. Starting with Mountain Lion (not sure) when I hold a character, instead of getting the usual character repetition, I got an annoying pop-up menu like this:
It only appears when you hold a character that could have an accent like åàáã and so forth.
I find this solution annoying for people that is quite fast at typing. I consider myself fast, so waiting for the pop-up menu to appear and then select the right character consumes too many milliseconds.
To stop that pop-up from appearing just open a terminal and type:
defaults write -g ApplePressAndHoldEnabled -bool NO
If you want it to come back type:
defaults write -g ApplePressAndHoldEnabled -bool YES
You have to close your app and open it again in order for this change to take effect, or just logout and login again.
How to write those accented characters? Simple key combinations. For example for US keyboards:
alt + e = ´ (áéíóú)
alt + ~ = ` (àèìòù)
alt + n = ˜ (ñã…)
alt + c = ç
Just to mention a few. Other keyboards might have a different combination, but I noticed that it’s almost the same. For example, the Japanese keyboard uses the (alt + _) to get ” ` ”
Once you get used to these combinations, it’s faster than using that pop-up menu.