But at what cost?
I'm all for JSON in many situations, especially where weight or client-side work is a concern, but moving away from XML loses readability (so important in those config files) and the power of tomorrow's problem solutions like XSLT and XPath. Be really sure why and when you move away: it's a de facto standard for a reason.
(aside: my habit is to use XML internally, and transform that to JSON where that's the desired output)
