The first niche is programming with XML. XQuery makes programming with
XML easier because it directly supports the things that matter most for
XML - construction, path expressions, and restructuring with FLWOR. This
is true of XSLT too, but (1) XSLT has not been successfully optimized
for large data stores, (2) some programmers don't wrap their brains
around XSLT, either because of the syntax or the heavily recursive
programming idioms.
The second niche is data integration, where the ability to translate
XQuery into other systems is very important.
XSLT is the Lisp of native XML programming. XQuery is ... more like a
SQL with report writing capabilities.
Jonathan
