Even on OS X it doesn't look great, but I'm guessing you're using Windows? Windows is notoriously bad at rendering custom fonts on Web pages for some reason. Enough so that some people stop custom fonts rendering on it using a JavaScript check.

Instapaper text: http://www.instapaper.com/text?u=http%3A%2F%2Fstatus.net%2F2...

I also find the font rather bad. It's very "skinny" and "tall".

Using Linux and Chromium here, no problem with the font.