I noticed that when deleting an answer, the shading doesn't appear until you hit refresh. The only indication it's deleted is the 'delete' text changing to the red 'undelete' which is subtle enough that I've wondered a couple times if I'd hit the 'delete' button (which is when I then look and see the 'undelete' text). Seems like it would be a pretty minor fix to have the shading implement immediately.
(This was using Firefox 3.5.7)