Here's a meaty article from CNET News on the latest XML developments. According to the co-creator of XML, Tim Bray, XML owes at least some of its success to its native support for Unicode. Here's a quote:

XML has succeeded, co-creator Bray said, because it has solved several of the more vexing challenges for electronic data exchange, including growing need to deal with diverse languages and character sets.

"One of the big problems is internationalization," Bray said. "One of the reasons XML took off is because it solved a lot of those issues with Unicode, which was fairly new at that point."

When XML hit the scene, HTML still advocated the Latin 1 character set and the Domain Name System was mired (and still is mired) in a subset of ASCII. Although HTML is now Unicode-friendly, XML was built to support the managing of the massive amounts of content that companies now struggle with. XML is far from perfect; because it is so flexible it allows for almost too much creativity from the vendors. Still, it's the best thing going and its support for Unicode has made XML the language for choice for companies that want to "future proof" their content.