I'm not sure about Ignore yet, for my use. I used it for the first time about a week ago, for two people that collectively pushed me over the edge. One of them started having meaningful comments again right away, for some strange reason, and I took that individual off ignore after a few minutes. The other's still there for now, and it's kinda nice.
I'm not sure if I'll use the function more or stop using it in the future. Probably use it on occasion for a very few people. Even trolls can be interesting, so I don't feel an urge to ignore most people. It's just if they're profoundly boring as well as angering, it's just not worth it.
In general though, I'm open to having my opinion changed about someone, but it takes a lot of positive factors after I form a strong negative opinion. That's often because people usually continue to act in similar ways, though. A douchebag today is more likely than not to be a douchebag tomorrow.