For example, a recent issue of the German magazine Java Spektrum discussed new XML technologies. Part of this is the difference between XML 1.0 and XML 1.1. And the question is: "is it important?"
This is a snippet from the Spec on W3C.org:
The overall philosophy of names has changed since XML 1.0. Whereas XML 1.0 provided a rigid definition of names, wherein everything that was not permitted was forbidden, XML 1.1 names are designed so that everything that is not forbidden (for a specific reason) is permitted. Since Unicode will continue to grow past version 4.0, further changes to XML can be avoided by allowing almost any character, including those not yet assigned, in names.
This sounds fundamental. Basically it means that (generally speaking) a well-formed XML 1.0 document is also well-formed in XML 1.1. But XML 1.1 documents are not necessarily well-formed in XML 1.0.
The next question is: who is waiting for the changes in XML 1.1. Aren't many people still using XML 1.0 for most purposes?
I think this depends on the language of your format. If you are designing a format with English tags, XML 1.0 is all you need. For languages like Dutch and German, XML 1.0 is still a reasonable choice. For languages using many special characters, things may be different.
From an Agile XML perspective... Is it more agile to design a format with tags in your own language / characters than it is to translate everything to English?