Sure its funny looking - smileys for comments, squiggly brackets all over the place and wacky operator words mixed with namespaces and code - but it sure does work.
And, whats more, as part of his Doctoral Thesis at the University of Utrecht, Joris Petrus Maria Graaumans has actual done some usability tests. He created a series of problems and then set people to solve them with SQL/XML, XSLT and XQuery.
Even though some people had little experience with XQuery it was overall more efficient and effective at solving problems, particularly as complexity increased.
See the report here (warning its big).
I think there are lots of reasons for this:
1. It still has powerful declarative capabilities with models for results, but you have a much finer degree of control - to start you can write your own regression to traverse the tree
2. It's also a lot like procedural languages and looks and feels a lot more like the most common languages out there so its easier to follow and invites you to create more complex code.
3. Well there should always be three points . . . so I guess mine is to try it! Check out the tutorial and see for yourself!