Jon:
Don't forget to us the [Mapping=tex-text] option as used below.
\documentclass{article}
\usepackage{xltxtra}
\setmainfont[Mapping=tex-text]{Palatino}
\begin{document}
Quoth the raven, ``Nevermore!''
\end{document}
--
United in adoration of Jesus,
fr. michael gilmary, mma