External configuration should be human-readable
For the love of all that is holy and good in the world make all of your external configuration readable and editable by human beings just in case I have to maintain your system later. Yeah, I know sometimes you have to encrypt configuration for those pesky security auditors, but at least make the unencrypted data readable. First of all, the mechanics of making little configuration tweaks shouldn't be difficult. Second, debugging and diagnosing problems is awfully difficult when you can't even read the configuration.
Xml by itself doesn't bother me, but I'm dealing with files that are partially SOAP serialized. "Simple" whatever protocol my ass. SOAP is not human readable!