This is how it looks.

I have the same problem (FF 19), but if you type "about:config" on adres bar and find "gfx.content.azure.enabled", then set this as "false" (duble click), then all text looks fine.

This problem started this week (week of 2/25) after I applied the Windows Platform Update. I have two Windows systems (one desktop, one laptop) and the fuzzy text only occurs on the laptop.

Disabling Azure as per the answer seems to have worked.

I've tried the solution and that fixed it for me as well, however in case developers need some more information about the issue, I recently saw the issue in the options menu of Firefox as well... which is rather strange.