Khaled Abou Alfa has a nice sum­mary of how the font ren­der­ing looks on the dif­fer­ent browsers (I believe this is all on Windows):

• Font Ren­der­ing

The way that Fire­fox ren­ders text on Win­dows is embar­rass­ing. It just looks ter­ri­ble. Using Alfa’s exam­ple, here is what the text looks like in Firefox:

Ouch. It hurts my eyes.