The slides for my XTech 2007 talk, My Stylesheet runs, but.., are now available from http://2007.xtech.org/public/schedule/detail/217.
Currently only an older version of my paper is available at that URL unfortunately.
One of the longstanding problems for xmlroff has been that Pango didn’t do justified text. Not anymore. The blog entry by Behdad Esfahbod at http://mces.blogspot.com/2007/05/justified-text-with-pango.html shows that it has been implemented, and once it’s in a Pango release, xmlroff will be able to use it.
I found that blog entry by looking for mentions of kashida support in Pango, and it looks like that could be in the works too.