Dear Joseph,
Following a bug report for (x)dvipdfmx box scaling, we are talking a look at xetex.def and dvidpfmx.def to fix that and related issues. This raises a question: what is the reason for having two .def files here. A quick test suggests that XeTeX (xdvipdfmx) can happily use dvipdfmx.def with the exception of a few lines at the end of the file: those could easily be made conditional.
I'm not familiar with the drivers, but I think that the independent xetex.def is definitely needed. I think that images png, jpg, pdf, are efficiently embedded in XeTeX, probably by using primitives, while dvipdfmx requires an external program extractbb to obtain sizes of the images. For example, % % xelatex test.tex (xetex.def) % \documentclass[12pt]{article} \usepackage{graphicx} \usepackage{pdfpages} \begin{document} \includepdf[pages={1-9}]{xtst.pdf} \end{document} is far faster than % % xelatex test.tex (dvipdfmx.def) % \documentclass[12pt,dvipdfmx]{article} \usepackage{graphicx} \usepackage{pdfpages} \begin{document} \includepdf[pages={1-9}]{xtst.pdf} \end{document} Best, Akira -------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex