Looking at my screen with a magnifying glass, it has no effect I can see on the browser fonts.
i've attached a png image to show how cleartype effects font rendering in google chrome on my system (windows xp professional sp3).
the example site is http://www.google.com/webfonts.on the left side you see the render with cleartype turned off and on the other side it is turned on. the differences are clearly visible.
mirko
<<attachment: cleartype-off-on-8bit.png>>
