But we can't always budget a nice configuration application.
And once we've just put simple XML file there for configuration and we're past the prototyping phase... "well this actually works good enough, let it be".
You likely need data model classes for the config anyway, along with support of serialization and deserialization (XML or not is not important). Use a stock property grid control, pass the root object of the config, and you’ll get a GUI that does the job much better than ASCII files.
And once we've just put simple XML file there for configuration and we're past the prototyping phase... "well this actually works good enough, let it be".