Reading the changelog for Bogofilter, a spam filtering tool, I spotted a note that, I think, should give a lesson to all XML unbelievers out there:
* The configuration file parser is stricter and more correct.
How long, I ask you, will the wheel get reinvented again and again? How many more incompatible, half-buggy, unsuitable for any off-the-shelf tools (if you don't count tedious and error-prone regex hacks in Perl), configuration formats we need? Why can't we just settle on XML, whatever its superficial flaws could be?