I’ve spent more time with other media than print lately, but this article on XML.com, Printing XML: Why CSS Is Better than XSL, is well worth the read.
I have no opinion of XSL-FO as a print formatter, relative to for instance Postscript. What I have noted is that the printer vendors have been working hard on using XHTML and CSS as printer drivers.
Now, if we were to get over the “printer-friendly version” habit…