I don't see why people can't be worried about someone who doesn't like Jean writing the character. As I've said all the times the subject is brought up, I don't think she HATES her or anything and will screw her over, but the fact that Jean is the first character that comes to mind every time someone asks who's her least favorite X-Men(or character in general? I'm not sure) is certainly not encouraging.
So, basically, while I'm not all that worried myself, I guess I'm tired of people bitching about how others are bitching and telling them to shut up lol.
I think people already explained what their problems were a few pages ago...