I'm managing fine without the ignore feature, but I'd like to have it. I can see how it would, in some cases, become obvious that you're ignoring someone, but I don't think it's guaranteed. And honestly, if a poster suddenly realizes that 20 people are ignoring her, maybe that should tell them something, you know?
The only person I would put on ignore doesn't post often, or at least we rarely end up in the same threads (for how infrequently I see her, for all I know she stopped posting ages ago). There's no learning to tolerate her - I just ignore her mentally instead of technologically. I don't think I have anything to learn from this one particular person that's worth the frustration of dealing with her, and I see her so infrequently (and usually in off-topic discussions) that I doubt there would ever be big quoting confusion issues.
There are a number of posters who I frequently disagree with, or who I'm just not terribly fond of, but in those cases, I do think we can learn from each other, and I wouldn't hide someone just because we don't get along.