Seriously? There are slight differences, but nowhere near the same extent as evidenced on OP's blog. Really, the only place I can see any difference is on the curve of the C's.

Side by side comparison: http://i.imgur.com/wYPr1rg.png

Some difference is to be expected. Google, Microsoft, and Firefox are in competition, after all. Microsoft has the advantage of controlling both the OS and the browser in this case. I would be surprised if IE did not render slightly better. As others have pointed out FF and Chrome look better on other OS's (where IE doesn't even play).