I'm starting this because there's another thread in Ubuntu +1. Users of 13.10 can feel free to post here and not worry about hijacking threads
I've been seeing one misformed letter per screen on Lubuntu 13.10 (clean install). It's mostly on Firefox beta. I'm not really sure if I've seen it with other apps.
If I highlight the letter by dragging the mouse cursor over it, the letter becomes perfect again.
If I press printscreen, the letter becomes perfect.
If I scroll the line off the screen and then bring it back, the letter appears perfect.