Well, I haven't experienced running into them and them actually being nice. I've seen them at the stores and stuff, and they still give me dirty looks (most of them are female, by the way) and act b*tchy. STILL. After all these years. It's pretty pathetic on their part. So, it's hard for me to say that I would be forgiving if they were nice to me now.
Also, I'm the type of person that holds a grudge. I NEVER forget, and forgiving is difficult for me. My boyfriend works in fast food and works with many people we went to school with that used to give us a really hard time. He'll tell me that this person and that person has changed, and they're no longer douche bags. As nice and true as that may be, it's hard for me to see them any differently. I knew them as assh*les, and that's all I know them as. If they were mean and awful to me before, I really don't have any interest in forgiving. Yeah, it's immature and I need to learn how to just let go and get over it. Blah blah blah. Most humans piss me off, anyway.