Cons:
harder for humans to read
harder for the program to parse
larger file size
requires lots of new code
requires that code to be debugged

As for your pros:

Clear and concise structure - what structure? If you just want to group a module's settings together, I would much prefer adding a simple block prefix.

Easy to standardize - new modules tend more and more to follow syntax from existing modules. XML only forces standardization that is already possible (and happening), and may hinder any new syntax that needs to be invented.

XML has its uses, config files are rarely among them IMO. (the module descriptions are another matter, that's a much better place to use XML)