[Tex/LaTex] XeTeX, microtype and fontspec

fontspecmicrotypeprotrusionxetex

I am using XeTeX from TL2010 with microtype 2.5 beta and fontspec. My main font is Linux Libertine O. I do not see a single difference with and without including the microtype package.

Am I doing something wrong, is there a better way to optimize character protrusion in XeTeX to get nicer paragraphs and spend less time fixing overfull lines?

This is what I'm doing:

% This line doesn't change anything at all
\usepackage[protrusion=true,final]{microtype}
\usepackage{fontspec}
\usepackage{xunicode}    
\setmainfont[Mapping=tex-text]{Linux Libertine O}                               
% other fonts and settings...

The logs do indicate that microtype seems to work:

LaTeX Info: Redefining \microtypecontext on input line 54.                      
Package microtype Info: Character protrusion enabled (level 2).                 
Package microtype Info: Using default protrusion set `alltext'.                 
Package microtype Info: No adjustment of tracking.                              
Package microtype Info: No adjustment of spacing.                               
Package microtype Info: No adjustment of kerning.  

Edit:
Actually, protrusion does work properly it seems, but it doesn't seem to help with overfull lines. Does protrusion not help with it, and is it only font expansion that helps with overfull lines?

Best Answer

After looking more closely, I do see that protrusion works (now that I know what it's supposed to do) and I understand that font expansion doesn't (yet) work with XeTeX. This question is thus solved.