While some teams over at Microsoft seem to think ClearType is so good that it deserves to be turned regardless of whether the user actually wanted it on, it seems that others don’t even have it turned on themselves.
Because if the Visual Studio team had ClearType turned on, they’d know that you always have to clear the background before you repaint your control.
Take a look at the “Start” page in Visual Studio 2005:
If I click on the “Recent Projects” text, it becomes this:
I did a “difference” of the two images (and, admittedly, I ramped the difference up a bit to make it more obvious), and got this:
So they’re obviously repainting the text without first clearing the background, and ClearType is writing it’s anti-aliased pixels twice. Yucky!