It doesn't quite seem to match the Typography section.
Where it says "We’re using Georgia for body text." and that they're using em for sizing it appears to be styled as "Helmet,Freesans,sans-serif;" and using px+% (like YUI).
Also main.css has 7 declarations at the top of just the font-size for html object - which looks weird. Deleting all but the declaration "html {font-size: 62.5%;}" appears to right-size the fonts for the page.
I can't see where the web-font is supposed to be being downloaded either but I've only taken a quick glance.
Edit:
Looks like it's browser specific - this is FF11 on Linux. Somehow not applying the @media declarations correctly? Also looks like the little script isn't giving me the fastfonts css.