Depends on what they did to you. There are some people that I'd wish for a far, far worse fate than pregnancy. But I digress. It's perfectly fine to adore Karma's little surprises like that.
No it just makes you weird. I was only ever happy once when I found out an ex was pregnant (also I really don't keep up with what going on with them you know), but that was because we really ended on ok terms and I had known she was really depressed for a while because she thought that she couldn't have kids, so much so that she was self-destructing. But when she did, it was good for her. I was happy in that way for her, but really I could sort of care less too.