I've recently switched to XeTeX. In my document I use this code to set the fonts:
\usepackage[math-style=ISO,bold-style=ISO]{unicode-math}
\usepackage{xunicode}
\usepackage{fontspec}
\defaultfontfeatures{Mapping=tex-text}
\setmainfont{Linux Libertine O}
\setsansfont{Linux Biolinum O}
\setmonofont{Inconsolata}
\setmathfont{XITS Math}
I installed Libertine and biolinium from the ubuntu repositories and I downloaded XITS and installed in my .fonts directory... Now I'd like to know what are the main differences between my approach and using the real latex packages (like libertineotf.)