You should be programming away from bad/worst case scenario not around assumptions about the end-user.
XML sure is terse and unweildy, no matter whether a human is used to it or not, the chances of things going wrong as a result of a "configuration error" when manually editing XML are high.
However, in the day and age of RAD, it's wise and definitely feasible to have a UI manage and maintain the configuration file(s), XML or otherwise.