As XML has become the lingua franca for text based data formats it is widely used in many applications of electronic document processing.
About diffing documents in XML-related formats some whitepapers are available for several years now (e.g. X-Diff). Since computing the 'optimal' difference between two XML documents is a matter of tree-to-tree comparison, many solutions deliver near-optimal and - even more important - ambiguous results.
1st of January: A test version of XTC 3.3.2 is now available for download.
A short introduction is also available here.