First, the automatic closing of characters (parenthesis, quotes, etc) seems like a cool feature to have as a lot of people like auto-closing characters, but I've found that the current support in ACE is too flaky for use in a production environment. There needs to be an option to turn this feature on/off.
Related issue: Automatic indentation is wildly inconsistent. There needs to be a separate option to turn this feature on/off.
Related bug: Selecting some spaces near the start of a line and pressing Tab on the keyboard doesn't replace the selected spaces with a tab - the auto-indent feature is probably getting in the way. The ACE demo has this problem too.