For field validation and conditional formatting, Self is a godsend. Another place it would be useful to have access to it would be in script parameters. If a field is set to execute a script, allow the use of Self in the script parameter. Currently when you try to do this, an error message of "This function cannot be used in this expression" is the result.
I'm sure they might be other places where Self is currently disallowed which might be useful to have. Anyone else?