Extending the list: (User vlozak - Jan 7, 2010) 

 * xsl syntax is extremely verbose, and xsl stylesheets can become very difficult to understand as a result. We have developed a significant code base of long xsl scripts for data and open document conversion, and only a small fraction of our IT staff have had the patience to work out how to maintain them. 

 * because of the vagaries of in-browser support xslt 2 in particular seems to be having problems gaining traction. This is disappointing as many of the xslt 2 specific numeric and text functions would greatly simplify xsl scripting. 

 * on the plus side xsl seems to be the most efficient scripting language for robustly and rapidly extracting fragments of knowledge from very complex xml data sets.