Great post but arrgh, use this to read it: http://lab.arc90.com/experiments/readability/
He also applied this to the body text: "font:140% 'Inconsolata', monospace;" I presume the site looks good in Inconsolata for those who have it installed.
This site is a good reminder to check your site on another computer. Also, make common font choices, or at least default to something specific that looks good.
This will give you support for most browsers (though it will muck up your CSS a bit)
EDIT: It's a good read, though, as noted above.
I just overrode letter-spacing in my browser's CSS debugger. Thanks for sharing that link.