I fall more in to your camp, Tomarctus. I have a lot of trouble holding grudges. At least, in any longterm sort of sense. It's just too easy to see why they did what they did—which doesn't mean I think it was okay that they did that, but I can almost never hold on to any anger with them. I'll be upset, but I always have an unbiased (and maybe too generous) impression of them floating around in the back of my head, even if I don't like them.
It doesn't mean I forgive the *action*, though. Or that I want to spend one single second in their company. In fact, I'll purposefully cut them off entirely, because I'm generally incapable of being anything but warm to people.
If there is anything I'll hold a grudge over, though, it will be when I feel something was just so inherently unjust that I can't stand it.