I really wish it wouldn't tell me that the ignored person has posted at all, that way I'm not even tempted to take them off of ignore for a second to read it. If I go as far as to ignore someone, which happens pretty rarely, I really want to forget they even exist on the forums.
Yeah, I still find myself reading some ignored posters. But at least then when I get angry I have no one but myself to blame.
The thing I wish it did was have an additional option to hide any post that is a reply to an ignored poster. Ignoring someone doesn't work so well when every post of theirs is just quoted anyway.